Monodisperse poly(p-chloromethylstyrene) microbeads by dispersion polymerization

In this study, an alternative dispersion polymerization method for the para isomer of chloromethylstyrene was proposed. Highly monodisperse poly(p-chloro-methylstyrene) (PCMS) particles in the size range of 1.67–3.75 μm were obtained. The monodispersity and the isolation yield of PCMS particles were significantly improved relative to the methods available in the literature. Azobisisobutyronitrile and polyacrylic acid were selected as the initiator and the steric stabilizer, respectively, in the dispersion medium composed of ethanol and methoxyethanol. The results indicated that the particle size increased with increasing initiator concentration. An increase in the stabilizer concentration led to a decrease in the particle size. The methoxyethanol/ethanol ratio was found as one of the most important parameters controlling the average size and the size distribution. Contrary to the tendencies noted in the literature, the particle size decreased with increasing polymerization temperature.     

Magnetohydrodynamic Natural Convection Flow in an Enclosure with a Finite Length Heater Using the Differential Quadrature (DQ) Method

Analysis of heat and fluid flow transport due to natural convection and magnetohydrodynamic (MHD) flows in a square enclosure with a finite length heater has been performed using the differential quadrature (DQ) technique. The heater with constant heat flux is located on the bottom wall of the enclosure and isothermal boundary conditions are applied to the right vertical wall while the remaining walls are adiabatic. The effects of heater length (0.2 ≤ ? ≤ 0.8), heater location (0.1 ≤ c/L ≤ 0.9), and direction of magnetic force (0° ≤ φ ≤ 90°) for different values of Grashof (10³ ≤ Gr ≤ 10⁶) and Hartmann numbers (0 ≤ Ha ≤ 100) on the heat and fluid flow in the enclosure are studied. According to the results obtained, heat transfer reduces when increasing the Hartmann number. The rate of reduction is higher for high values of Grashof number. The heat transfer rate for the heater closer to the cold wall is considerably higher than the heaters far from the right wall.     

Comparative evaluation of full‐scale UASB reactors treating alcohol distillery wastewaters in terms of performance and methanogenic activity

In this study, two full‐scale upflow anaerobic sludge blanket (UASB) reactors, namely TUASB and CUASB, at the wastewater treatment plants of the Tekirdaǧ Alcohol (Raki) and Canakkale Alcohol (Cognac) distilleries were investigated in terms of performance, acetoclastic methanogenic capacity and microbial composition. The results were compared with a previously studied other UASB reactor (IUASB) at the wastewater treatment plant of the Istanbul Alcohol (Raki) Distillery from which the two reactors (TUASB and CUASB) were seeded. The IUASB reactor performed well achieving COD removal efficiencies of no lower than 85% at organic logding rates (OLRs) in the range of 6–11 kg COD m⁻³ day⁻¹ between 1996 and 2001. During the last one year of operation, between 2000 and 2001, performance of the CUASB reactor in terms of COD removal efficiency was 70–80% at OLRs in a range of 1–4.5 kg COD m⁻³ day⁻¹ whereas it was 60–80% at OLRs in a range of 2.5–8.5 kg COD m⁻³ day⁻¹ in the TUASB reactor. At the end of year 2000, specific methanogenic activity (SMA) tests were carried out to determine potential loading capacity and optimum operating conditions of the IUASB, CUASB and TUASB reactors. The potential methane production (PMP) rates of the CUASB, IUASB and TUASB reactors were measured as 230 cm³ CH₄ gVSS⁻¹ day⁻¹, 350 cm³ CH₄ gVSS⁻¹ day⁻¹ and 376 cm³ CH₄ gVSS⁻¹ day⁻¹ respectively. When the PMP rates were compared with actual methane production (AMP) rates obtained from the three UASB reactors, AMP/PMP ratios were evaluated to be 0.18, 0.12 and 0.13 for CUASB, TUASB and IUASB reactors respectively. This showed that the CUASB, TUASB and IUASB reactors were using only 18%, 12% and 13% of their potential acetoclastic methanogenic capacity respectively. These results can be interpreted that the three UASB reactors were underloaded compared with their potential acetoclastic methanogenic capacities. It was, therefore, recommended that the three UASB reactors should be loaded at higher organic loading rates or sludge withdrawn in order to maintain an AMP/PMP ratio of 0.6–0.7, which can ensure desired reactor performance with safer operation. Results of epifluoresence microscopic examinations showed that the percentage of total autofluorescent methanogens was approximately 30% of the total population in sludges from the TUASB and IUASB reactors whereas it was 20% in sludge from the CUASB reactor. The two UASB reactors treating raki distillery wastewaters contained sludges having a higher percentage of autofluorescent methanogenic population and higher acetoclastic methanogenic activity. Copyright © 2004 Society of Chemical Industry     

Challenges in Developing a Bessel-Beam Based Ultrafast Ablation Probe

Instruments and Experimental Techniques - With its elongated depth of focus, Bessel beams offer rapid and high aspect ratio ablation capability, in contrast to Gaussian beam counterparts. In this...     

Utilization of Catalytic Properties of the Encapsulated Lipase with Calix[4]arene-Adorned Sporopollenin

The dihydrazide calix[4]arene was immobilized onto sporopollenin in order to encapsulate Candida rugosa lipase (CRL) via sol-gel entrapment. The kinetic resolution of the new encapsulated lipase was investigated for enantioselective hydrolysis of racemic naproxen methyl ester and 2-phenoxypropionic acid methyl ester. The results demonstrated that the activity and enantioselectivity of the lipase were improved when the lipase was encapsulated in the presence of calix[4]arene-immobilized sporopollenin. The encapsulated lipase showed an excellent rate of enantioselectivity against the (R/S)-naproxen methyl and (R/S)-2-phenoxypropionic acid methyl esters, with E = 350 and 295, respectively, compared to the free enzyme.     

Prediction of the colorimetric parameters and mass loss of heat‐treated bamboo: Comparison of multiple linear regression and artificial neural network method

In this study, the colorimetric parameters (L*, a*, b*) and mass loss of heat‐treated bamboo were investigated, and the obtained results were modeled by using two methods: multiple linear regression (MLR) and artificial neural network (ANN). First, bamboo samples were exposed to heat treatment at different temperatures (110°C, 140°C, 170°C, and 200°C) and durations (15, 30, 45, 60, 75, 90, and 115 minutes) in a laboratory oven. Then, the colorimetric parameters (L*, a*, b*) and mass loss of each sample were measured after each period of heat treatment. All data were modeled by using two methods separately for each parameter and the performances of these proposed methods were compared. It was found that color change and mass loss increased with increasing temperature and duration of heat treatment. Mean absolute percentage error (MAPE) values of all obtained MLR ranged from 0.64% to 10.63%, while the all MAPE values of ANN were found to be lower than 1.5%. Based on these results, it can be said that MLR and ANN could be used to evaluate the changes on the selected properties of heat‐treated bamboo samples. On the other hand, it should be emphasized that the ANN gave more accurate results than the MLR method because of its learning capability.     

Raman Spectroscopic Barcode Use for Differentiation of Vegetable Oils and Determination of Their Major Fatty Acid Composition

In this study, differentiation of vegetable oils and determination of their major fatty acid (FA) composition were performed using Raman spectral barcoding approach. Samples from seven different sources (sunflower, corn, olive, canola, mustard, soybean and palm) were analyzed using Raman spectroscopy. Second derivative of the spectral data was utilized to generate unique barcodes of oils. Chemometric analyses, namely, principal component analysis (PCA) and partial least square (PLS) methods were used for data analysis. PCA was applied for classification of the samples according to the differences in their levels arising from their barcode data. A successful differentiation based on second derivative barcodes of Raman spectra (2D‐BRS) of vegetable oils was obtained. In addition, PLS method was applied on 2D‐BRS in order to determine the major FA composition of these samples. Coefficient of determination values for palmitic, stearic, oleic, linoleic, α‐linolenic, cis‐11 eicosenoic, erucic and nervonic acids were in the range of 0.970–0.989. Limit of detection and limit of quantification values were found to be satisfactory (0.09–8.09 and 0.30–26.95 % in oil) for these fatty acids . Advantages of both chemometric analysis and spectral barcoding approach have been utilized in the present study. Taking the second derivative of the Raman spectra has minimized background variability and sensitivity to intensity fluctuations. Spectral conversion to the barcodes has further increased the quality of information obtained from Raman spectra and also made it possible to improve the visualization of the data. Converting Raman spectra of oils into barcodes enables simpler presentation of the valuable information, and still allows further analysis such as classification of vegetable oils and prediction of their major fatty acids with high accuracy.