5-Hydroxymethylfurfural (HMF) formation during subcritical water extraction

The aim of this study was to investigate the effect of material type (artichoke leave, lemon peel, flaxseed meal), extraction temperature (50, 100, 120, 140, 160, 180, 200 °C) and static extraction time (5, 15, 30, 45 min) on 5-hydroxymethylfurfural (5-HMF) formation during subcritical water extraction. 5-HMF content of artichoke leave and lemon peel extracts increased 7.2 and 26.1 times with the rise of extraction temperature from 160 to 180 °C for 5 min during subcritical water extraction, respectively. Besides, 5-HMF content of artichoke leave, lemon peel and flaxseed meal extracts increased 1.4, 2.0 and 4.5 times as static extraction time increased from 15 to 45 min at 180 °C during subcritical water extraction, respectively. The highest 5-HMF content of artichoke leave and lemon peel extracts were obtained as 58.83 and 231.21 mg/L at 180 °C and 45 min, respectively. However, for flaxseed meal, the highest 5-HMF content (222.94 mg/L) was obtained at 200 °C and 15 min during subcritical water extraction.     

Determination of CaCO<Subscript>3</Subscript> and SiO<Subscript>2</Subscript> content in the binders of historic lime mortars

The binders of historic mortars composed of small grain sized silica (SiO₂) and carbonated lime (CaCO₃) are considered as the main part that give hydraulic character and high strength to the mortar. In this study, FTIR, SEM–EDS, LIBS and XRD spectroscopy were used to find out the weight ratios of CaCO₃ to SiO₂ in the binders of historic lime mortars. For this purpose, a series of pure calcium carbonate and silica mixture were prepared in ten combinations in varying ratios from 0.5 to 5. Calibration curve was prepared for each analysis by plotting the peak area or intensity ratios of CaCO₃ to SiO₂ versus the weight ratios of CaCO₃ to SiO₂. A good linear correlation coefficient was obtained for each analysis respectively. The analyses were then tested on the binder of the Roman mortar samples. The results indicated that FTIR, SEM–EDS and LIBS spectroscopy are convenient tools to determine the weight ratios of CaCO₃ to SiO₂ in the binders of mortars. But XRD spectroscopy is not convenient for quantitative analysis of binders due to the presence of varied amounts of amorphous or poor crystalline silica in their compositions.     

Turbulence effect on transmittance of atmospheric optics telecommunication system using dense wavelength division multiplexing

The effect of atmospheric turbulence on atmospheric optics telecommunication links employing dense wavelength division multiplexing (DWDM) systems is examined. For this purpose, transmittance obtained by using the MODTRAN (MODerate resolution atmospheric TRANsmission) code is modified by the transmittance due to turbulence when the incidence is a partially coherent optical beam. The spanned wavelengths cover the range employed in a practical DWDM system operating in the range of 1550?nm. The effect of turbulence is manifest as a decrease in the transmittance calculated by MODTRAN, being more effective when the incidence becomes less coherent.