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51.
Aysel Kantürk Figen Pınar Yilmaz Atali Mehmet Burçin Pişkin 《Journal of Thermal Analysis and Calorimetry》2014,118(1):31-42
In this study, the thermal behavior in terms of glass transition (T g), degradation, and thermal stability of four commercial new-generation posterior bulk fill composites (Surefill SDR, Dentsply; Quixfill, Dentsply; Xtrabase, Voco; and Xtrafill, Voco) activated by light-emitting diodes (LEDs) was analyzed by thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The activation energies (E a) for the decomposition of the dental resins were calculated based on the Kissinger and Doyle kinetic models from the peaks of the endothermic curves obtained when the specimens were heated at four different temperatures (5, 10, 15, and 20 °C min?1) during DSC. The results show that the Xtrabase composite displayed the highest T g (120 °C at a 5 °C min?1 heating rate) and E a (157.64 kJ mol?1) values associated with thermal degradation from the main chain of the polymer. 相似文献
52.
This article presents a Taylor collocation method for the approximate solution of high‐order linear Volterra‐Fredholm integrodifferential equations with linear functional arguments. This method is essentially based on the truncated Taylor series and its matrix representations with collocation points. Some numerical examples, which consist of initial and boundary conditions, are given to show the properties of the technique. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011 相似文献
53.
Nilay Akgnüllü Niyazi ahin Mehmet Sezer 《Numerical Methods for Partial Differential Equations》2011,27(6):1707-1721
In this study, a Hermite matrix method is presented to solve high‐order linear Fredholm integro‐differential equations with variable coefficients under the mixed conditions in terms of the Hermite polynomials. The proposed method converts the equation and its conditions to matrix equations, which correspond to a system of linear algebraic equations with unknown Hermite coefficients, by means of collocation points on a finite interval. Then, by solving the matrix equation, the Hermite coefficients and the polynomial approach are obtained. Also, examples that illustrate the pertinent features of the method are presented; the accuracy of the solutions and the error analysis are performed. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 27: 1707–1721, 2011 相似文献
54.
Mehmet Naci Özer 《Applied mathematics and computation》2011,218(5):2277-2280
We perform a multiple-time scales analysis and compatibility condition to the regularized long-wave (RLW) equation. We derive Korteweg-de Vries (KdV) flow equation in the bi-Hamiltonian form as an amplitude equation. 相似文献
55.
Gizem Kaleli‐Can Busra Ozlu Hatice Ferda
zgüzar Baran Onal‐Ulusoy Gzde Kabay Taesik Eom Bong Sup Shim Mehmet Mutlu 《Electroanalysis》2020,32(8):1696-1706
A biosensor was prepared with natural melanin nanoparticles (MNP) decorated on a screen‐printed carbon electrode (SPCE). Hexavalent chromium was selected as a well‐known heavy metal ion to be detected for testing the performance of novel biosensor. Natural MNP was extracted from cuttlefish (Sepia officinalis) ink. Surface decoration of SPCEs with MNP was performed by two different methods. The first one was layer‐by‐layer assembly (LBL‐A) for different cycle times(n). In the second one, plasma treatment of SPCE incorporated with evaporation‐induced self‐assembly (EI‐SA) techniques including different incubation times in MNP solutions. The performance of both modified SPCEs were tested for amperometric detection of Cr(VI) in various water samples, and peak reduction of Cr(VI) was determined at 0.33 V. Amperometric results showed wide linear ranges of 0.1–2 μM and 0.1–5 μM of Cr(VI) for SPCEs modified with 14n‐LBL‐A and 12h‐EI‐SA, respectively. The sensitivities of SPCEs modified with 14n‐LBL‐A and 12h‐EI‐SA techniques were 0.27 μA μM?1 and 0.52 μA μM?1, respectively. In addition, both modified SPCEs selectively detected Cr(VI) in a model aqueous system composed of certain other heavy metals and minerals, and tap and lake water samples. The LOD and LOQ values for 12h‐EI‐SA were 0.03 μM and 0.1 μM, respectively. This showed that MNP‐modified‐SPCEs generated via EI‐SA techniques have the potential to be an alternative to conventional detection methods such as ICP‐MS. 相似文献
56.
Kenan Can Tok Mehmet Gumustas Giorgi Jibuti Halit Sinan Suzen Sibel A. Ozkan Bezhan Chankvetadze 《Molecules (Basel, Switzerland)》2020,25(24)
In a recent study, opposite enantiomer elution order was observed for ketoprofen enantiomers on two amylose-phenylcarbamate-based chiral columns with the same chemical composition of the chiral selector but in one case with coated while in the other with an immobilized chiral selector. In the present study, the influence of this uncommon effect on method validation parameters for the determination of minor enantiomeric impurity in dexketoprofen was studied. The validated methods with two alternative elution orders for enantiomers were applied for the evaluation of enantiomeric impurity in six marketed dexketoprofen formulations from various vendors. In most of these formulations except one the content of enantiomeric impurity exceeded 0.1% (w/w). 相似文献
57.
In this work, we performed density functional calculations to examine the molecular adsorption states of thiophene on β-SiC(0 0 1)-2×1 surface. A number of possible adsorption geometries are considered into two groups as the polymeric thiophene chain and the individual molecules covalently bonded onto the surface. The results show that the polymeric chain on the surface is the less stable adsorption case and individual arch like adsorption case structure is more stable than others. In all adsorption cases, the adsorbed SiC surfaces are characterized as different semiconductors. 相似文献
58.
Abdurrahman Özhan Ömer Şahin Mehmet Maşuk Küçük Cafer Saka 《Cellulose (London, England)》2014,21(4):2457-2467
In this work, activated carbon prepared from pine cone (PCAC) with ZnCl2 as an activation agent under microwave radiation was investigated. The activation step was performed at the microwave input power of 400 W and radiation time of 5 min. The properties of activated carbon were characterized by N2 adsorption Brunauer–Emmett–Teller (BET), scanning electron microscopy and Fourier transform infrared spectroscopy. Results showed that the BET surface area, Langmuir surface area, and total pore volume of PCAC were 939, 1,486 m2/g and 0.172 cm3/g, respectively. Adsorption capacity was demonstrated by the iodine numbers. The adsorptive property of PCAC was tested using methylene blue dye. Equilibrium data was best fitted by the Langmuir isotherm model, showing a monolayer adsorption capacity of 60.97 mg/g. The pseudo-first- and pseudo-second-order kinetic models were examined to evaluate the kinetic data, and the rate constants were calculated. Adsorption of the dyes followed pseudo-first order kinetics. Thermodynamic parameters such as free energy, enthalpy and entropy of dye adsorption were obtained. 相似文献
59.
Ultrasound-assisted emulsification-microextraction (USAEME) procedure was developed for the determination of selected polychlorinated biphenyls (PCBs) in 10 mL of water samples by gas chromatography-mass-selective detection. After determination of the most suitable solvent and extraction time, several other parameters including solvent volume, centrifugation time and ionic strength of the sample were optimized using a 23 factorial experimental design. The optimized USAEME procedure used 200 μL of chloroform as extraction solvent, 10 min of extraction with no ionic strength adjustment at 25 °C and 5 min of centrifugation at 4000 rpm. The limits of detection ranged from 14 ng L−1 (for PCB153) to 30 ng L−1 (for PCB101). Recoveries of PCBs from fortified distilled water are over 80% for three different fortification levels between 0.1 and 5 μg L−1 and relative standard deviations of the recoveries are below 10%. The performance of the proposed method was compared with those involving traditional liquid-liquid extraction (LLE) and solid phase extraction (SPE) on the real water samples (i.e., tap and well water as well as domestic and industrial wastewaters, etc.) and comparable efficiencies were obtained. The proposed USAEME procedure has been demonstrated to be viable, simple, rapid and easy to use for residue analysis of PCBs in water samples. 相似文献
60.
Gas chromatography-mass spectrometry (GC-MS) and liquid chromatography with fluorescence detection (LC-FL) methods have been proposed for the determination of low level nitrite and nitrate in biological, food and environmental samples. The methods include derivatization of aqueous nitrite with 2,3-diaminonaphthalene (DAN), enzymatic reduction of nitrate to nitrite, extraction with toluene and chromatographic analyses of highly fluorescent 2,3-naphthotriazole (NAT) derivative of nitrite by using GC-MS in selected-ion-monitoring (SIM) mode and LC-FL. Nitrite and nitrate ions in solid samples were extracted with 0.5 M aqueous NaOH by sonication. The recoveries of nitrite and nitrate ions based on GC-MS and LC-FL results were 98.40% and 98.10% and the precision of these methods, as indicated by the relative standard deviations (RSDs) were 1.00% for nitrite and 1.20% for nitrate, respectively. The limits of detection of the GC-MS in SIM mode and LC-FL methods based on S/N = 3 were 0.02 and 0.29 pg/ml for nitrite and 0.03 and 0.30 pg/ml for nitrate, respectively. 相似文献