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91.
Ekrem Köksal Ercan Bursal İlhami Gülçin Mustafa Korkmaz Cüneyit Çağlayan Ahmet C. Gören 《International Journal of Food Properties》2017,20(3):514-525
Like tea, the leaves of Turkish thyme (Thymus vulgaris) can be boiled in water to produce an extract. This is widely used as syrup for the treatment of coughs and bronchitis at alternative medicine clinics in many parts of the world. In the current study, we assessed the phenolic content and antioxidant activity of thyme. The antioxidant activities of both ethanol and aqueous extracts of thyme were determined using various in vitro methods. The total phenolic and total flavonoid contents were determined to be a gallic acid equivalent and a quercetin equivalent, respectively. Finally, the quantities of the phenolic compounds were detected using high-performance liquid chromatography and tandem mass spectrometry. The total phenolic compounds in the aqueous extract and ethanol extracts of Turkish thyme were 256.0 μg gallic acid equivalent/mg dried extract and 158.0 μg gallic acid equivalent/mg dried extract, respectively. Conversely, the total flavonoid compounds in both extracts were 44.2 μg and 36.6 μg quercetin equivalent/mg dried extract, respectively. For the first time, we determined phenolic contents and investigated the antioxidant potential of thyme. The results indicate that Turkish thyme is a good dietary source with phenolic properties. 相似文献
92.
Medine Güllüce Münevver Skmen Fikrettin ahin Atalay Skmen Ahmet Adigüzel Hakan
zer 《Journal of the science of food and agriculture》2004,84(7):735-741
The in vitro antimicrobial and antioxidant activities of the essential oil and methanolic extract of Micromeria fruticosa ssp serpyllifolia as well as the composition of the essential oil were examined. The essential oil exhibited activity against 14 bacteria, three fungi and a yeast, with minimal inhibitory concentration (MIC) values ranging from 31.25 to 125 µl ml?1, whilst the methanolic extract was inactive. Antioxidant activity was measured by two methods, namely scavenging of the free radical DPPH and inhibition of linoleic acid oxidation. The methanolic extract exhibited significant antioxidant activity in both assays, providing 50% inhibition at 70.9 ± 0.5 µg ml?1 concentration in the DPPH assay and inhibiting linoleic acid oxidation to 59% at 2 mg ml?1 concentration, whilst the essential oil showed activity only at higher concentrations. The gallic acid equivalent total phenolic content of the methanolic extract was found to be 55.2 ± 2.00 µg mg?1 dry weight extract (5.5% w/w). The chemical composition of the hydrodistilled essential oil was analysed by means of GC/MS. Twenty‐nine constituents were identified, the main ones being piperitenone (50.61%) and pulegone (29.19%). Copyright © 2004 Society of Chemical Industry 相似文献
93.
Ahmet Rizaner Ali H. Ulusoy Hasan Amca Kadri Hac?o?luAuthor vitae 《Computers & Electrical Engineering》2011,37(6):1082-1089
Multiple access interference (MAI) is the main factor affecting the performance of channel estimation techniques for code division multiple access (CDMA) systems. Although, several multi-user channel estimation algorithms have been proposed to mitigate MAI, these algorithms require high computational complexities. In this paper, we address the problem of iterative least squares (LS) mobile channel estimation at high channel efficiency that requires a short training sequence along with the spreading sequences. We employ an efficient iterative method based on conjugate gradient (CG) algorithm to reduce the computational complexity of the estimation method. Computer simulations illustrate that the proposed method performs almost identical to the exact LS estimate for reasonable training lengths. 相似文献
94.
Cem Topkaya Ahmet Serhat Kalayc? Eric B. Williamson 《Canadian Metallurgical Quarterly》2008,13(4):418-424
A study has been undertaken to investigate different solver and shell element performances for curved bridge finite-element analysis. Three sparse solvers were implemented into a bridge finite-element analysis code, and the solution times and memory requirements for typical bridges were compared. In addition, the use of four-node and nine-node shell elements in modeling was investigated for different mesh densities. Based on the comparative studies performed, modeling guidelines for practicing engineers have been developed and are presented herein. 相似文献
95.
Musharaf Muhammad Karamat Shumaila Hassan Muhammad Umair Khalique Uzma Oral Ahmet Behjat Arash Badami Akram Rizwan Almohaimeed Ziyad 《Journal of Superconductivity and Novel Magnetism》2021,34(10):2633-2642
Journal of Superconductivity and Novel Magnetism - Crystalline ZnO offers an excellent host matrix to create a dilute magnetic semiconductor (DMS) owing to its facile Zn-atom substitution with the... 相似文献
96.
97.
A series of poly(styrene-co-allyalcohol)-graft-stearic acid copolymers were synthesized as novel polymeric solid–solid phase change materials (SSPCMs). The graft copolymerization reactions between poly(styrene-co-allyalcohol) and stearoyl chloride were verified by Fourier transform infrared (FT-IR) and Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy techniques. The crystal morphology of the SSPCMs was investigated using polarized optical microscopy (POM) technique. Thermal energy storage properties of the synthesized SSPCMs were measured using differential scanning calorimetry (DSC) analysis. The POM results showed that the crystalline phase of the copolymers transformed to amorphous phase above their phase transition temperatures. Thermal energy storage properties of the synthesized SSPCMs were investigated by differential scanning calorimetry (DSC) and found that they had typical solid–solid phase transition temperatures in the range of 27–30 °C and high latent heat enthalpy between 34 and 74 J/g. Especially, the copolymer with the mole ratio of 1/1 (poly(styrene-co-allyalcohol)/stearoyl chloride) is the most attractive one due to the highest latent heat storage capacity among them. The results of DSC and FT-IR analysis indicated that the synthesized SSPCMs had good thermal reliability and chemical stability after 5000 thermal cycles. Thermogravimetric (TG) analysis results suggested that the synthesized SSPCMs had high thermal resistance. In addition, thermal conductivity measurements signified that the synthesized PCMs had higher thermal conductivity compared to that of poly(styrene-co-allyalcohol). The synthesized copolymers as novel SSPCMs have considerable potential for thermal energy storage applications such as solar space heating and cooling in buildings and greenhouses. 相似文献
98.
Large-scale energy storage methods can be used to meet energy demand fluctuations and to integrate electricity generation from intermittent renewable wind and solar energy farms into power grids. Pumped hydropower energy storage method is significantly used for grid electricity storage requirements. Alternatives are underground storage of compressed air and hydrogen gas in suitable geological formations. Underground storage of natural gas is widely used to meet both base and peak load demands of gas grids. Salt caverns for natural gas storage can also be suitable for underground compressed hydrogen gas energy storage. In this paper, large quantities underground gas storage methods and design aspects of salt caverns are investigated. A pre-evaluation is made for a salt cavern gas storage field in Turkey. It is concluded that a system of solar-hydrogen and natural gas can be utilised to meet future large-scale energy storage requirements. 相似文献
99.
Yakup Kaya Nizamettin Kahraman Ahmet Durgutlu Behçet Gülenç 《Metallurgical and Materials Transactions A》2017,48(8):3721-3733
Grade A ship-building steel-AISI 2304 duplex stainless steel composite plates were manufactured via explosive welding. The AISI 2304 plates were used to clad the Grade A plates. Optical microscopy studies were conducted on the joining interface for characterization of the manufactured composite plates. Notch impact, tensile-shear, microhardness, bending and twisting tests were carried out to determine the mechanical properties of the composites. In addition, the surfaces of fractured samples were examined by scanning electron microscopy (SEM), and neutral salt spray (NSS) and potentiodynamic polarization tests were performed to examine corrosion behavior. Near the explosion zone, the interface was completely flat, but became wavy as the distance from the explosion zone increased. The notch impact tests indicated that the impact strength of the composites decreased with increasing distance from the explosion zone. The SEM studies detected brittle behavior below the impact transition temperature and ductile behavior above this temperature. Microhardness tests revealed that the hardness values increased with increasing distance from the explosion zone and mechanical tests showed that no visible cracking or separation had occurred on the joining interface. The NSS and potentiodynamic polarization tests determined that the AISI 2304 exhibited higher corrosion resistance than the Grade A steel. 相似文献
100.
Nedim Muzoğlu Ahmet Mesrur Halefoğlu Muhammed Onur Avci Melike Kaya Karaaslan Bekir Sıddık Binboğa Yarman 《Expert Systems》2023,40(1):e13141
Since the first case of COVID-19 was reported in December 2019, many studies have been carried out on artificial intelligence for the rapid diagnosis of the disease to support health services. Therefore, in this study, we present a powerful approach to detect COVID-19 and COVID-19 findings from computed tomography images using pre-trained models using two different datasets. COVID-19, influenza A (H1N1) pneumonia, bacterial pneumonia and healthy lung image classes were used in the first dataset. Consolidation, crazy-paving pattern, ground-glass opacity, ground-glass opacity and consolidation, ground-glass opacity and nodule classes were used in the second dataset. The study consists of four steps. In the first two steps, distinctive features were extracted from the final layers of the pre-trained ShuffleNet, GoogLeNet and MobileNetV2 models trained with the datasets. In the next steps, the most relevant features were selected from the models using the Sine–Cosine optimization algorithm. Then, the hyperparameters of the Support Vector Machines were optimized with the Bayesian optimization algorithm and used to reclassify the feature subset that achieved the highest accuracy in the third step. The overall accuracy obtained for the first and second datasets is 99.46% and 99.82%, respectively. Finally, the performance of the results visualized with Occlusion Sensitivity Maps was compared with Gradient-weighted class activation mapping. The approach proposed in this paper outperformed other methods in detecting COVID-19 from multiclass viral pneumonia. Moreover, detecting the stages of COVID-19 in the lungs was an innovative and successful approach. 相似文献