Effects of B2O3 addition on structural and dielectric properties of PVDF

α‐Crystalline form of PVDF doped with Boron oxide (B₂O₃₎ composite films were produced between 0.2 and 1% weight ratio via the casting procedure. This low‐level doping rate did not change the crystalline structure of PVDF; however, they increased the lower and upper glass transition temperatures, which are associated with the amorphous ratio of polymer. This increment was found to be the highest for the sample 0.8% B₂O₃‐doped PVDF as 25 and 9.7%, respectively. Because of the low specific volume occurred in the 0.8% doped sample, B₂O₃ molecules are closer to the side groups of PVDF and, therefore, the coordination bonds also occurred according to the interaction between them and as a result of this interaction a geometric deformation occurred on the morphology of B₂O₃. In consequence of this deformation, morphology of B₂O₃ gained net dipole moment and provided a contribution to the dipole moment density of the structure. Hence, higher dielectric constant values obtained than that of pure PVDF. At 1 kHz and 300 K, the real dielectric constant increased by 236% compared to that of pure PVDF. It was shown experimentally by the 0.8% doping level of B₂O₃ that decreasing porous and gap structure resulted a high dielectric constant. POLYM. ENG. SCI., 54:2536–2543, 2014. © 2013 Society of Plastics Engineers     

Dark fermentative hydrogen production from sucrose and molasses

There are many factors affecting the dark fermentative hydrogen production. The interaction of these factors, that is, their combined effects, should be investigated for better design of the systems with stable and higher hydrogen yields. This study aimed to investigate the combined effects of initial substrate, pH, and biomass (or initial substrate to biomass) values on hydrogen production from sucrose and sugar‐beet molasses. Therefore, optimum initial chemical oxygen demand (COD), pH, and volatile suspended solids (VSS) or initial substrate to biomass (VSS) ratio (S/X_o) values leading to the highest dark fermentative hydrogen production were investigated in batch reactors. An experimental design approach (response surface methodology) was used. Results revealed that when sucrose was the substrate, maximum hydrogen production yield (HY) of 2.3 mol H₂/mol sucrose_added was obtained at initial pH of 7 and COD of 10 g/L. Initial S/X_o values studied (4–20 g COD/g VSS) had no effect on HY, while the initial pH was found as the parameter mostly affecting both HY and hydrogen production rate (HPR). When substrate was molasses, initial COD concentration was the only variable affecting HY and HPR. Maximum of both was achieved at 10 g/L initial COD. Initial VSS values studied (2.5–7.5 g/L) had no effect on HPR and HY. This study also indicated that molasses leads to homoacetogenesis for potentially containing intrinsic microorganism and/or natural constituents; thus, sucrose is more advantageous for hydrogen production via fermentation. Homoacetogenesis should be prevented for effective optimization via response surface methodology, if substrate is a natural carbon source potential to have intrinsic microorganisms. Copyright © 2017 John Wiley & Sons, Ltd.     

Improvement of enzymatic xylooligosaccharides production by the co-utilization of xylans from different origins

This study aimed to improve XOs production by enzymatic hydrolysis of xylans from various lignocellulosic waste biomasses namely corn cob, cotton and sunflower stalks, rice hull, wheat straw by using two commercial xylanase preparations, Shearzyme 500L and Veron 191. Shearzyme 500L showed better xylan hydrolysis capacity with high amount of xylose liberation. Xylobiose was the main hydrolysis product in each case. Even though the enzymatic hydrolyses using Shearzyme 500L resulted higher reducing sugar production compared to those of Veron 191, the hydrolysis of complex xylan structures was improved and the production of undesirable xylose was lowered by the co-utilization of xylanase preparations. By the co-utilization of xylanase preparations, the reducing sugar production from wheat straw, corn cob and sunflower stalk originated xylans was increased by 36%, 33% and 13%, respectively, compared to the expected reducing sugar yields. The highest reducing sugar production was obtained from complex corn cob xylan. The depolymerization of cotton and sunflower stalk xylan was poorest even though they have simple structures. Poor utilization of these xylans might be related to their high residual lignin content which might hinder the accessibility of xylan by the xylanases. However, the utilization of sunflower and cotton stalk xylan was improved when they were hydrolyzed within a xylan mixture containing equal amounts of each of five different xylans. In short, XOs production efficiency from agricultural waste materials was improved by the co-utilization of suitable xylanase and/or xylan mixtures considering the heterogeneous structures of xylan and different substrate specificities of xylanases.     

Inverse microemulsion copolymerization of butyl acrylate and acrylamide: kinetics,colloidal parameters and some model applications

The inverse microemulsion copolymerization of acrylamide and butyl acrylate initiated by ammonium peroxodisulphate, a water‐soluble initiator, and stabilized by anionic emulsifiers sodium bis‐2‐ethylhexylsulfosuccinate and sodium dodecylsulphate (SDS) has been studied. An increase of SDS concentration was observed to increase both the rate of polymerization and the particle size. The average number of radicals per particle (n?) is much below 0.5, which indicates desorption of monomeric radicals from polymer particles. The exit (desorption) rate constants k′_des (cm² s^?1) and k_des (s^?1) were evaluated as a function of SDS concentration (or the particle size) according to the Ugelstad/O'Toole (I), Nomura (II) and Gilbert (III) models. The value of k_des (s^?1) decreases with increasing particle size (or SDS concentration) for all three (I, II and III) models. A complex trend appears for k′_des (cm² s^?1): the Ugelstad/O'Toole model estimates a decrease, the Nomura model finds no variation and the Gilbert model estimates even a slight increase in k′_des with increasing SDS concentration. Copyright © 2006 Society of Chemical Industry     

Knowledge,attitudes and self-reported practices of food service staff regarding food hygiene in Edirne,Turkey

The purpose of this study was to evaluate the knowledge, attitudes and practices among food service staff with regards to food hygiene in hospitals in Edirne, Turkey, and to provide baseline data for implementing HACCP in hospital food services by carrying out a questionnaire by a face-to-face interview. The current study shows that food service staff in Edirne hospitals have insufficient knowledge regarding the basics of food hygiene. And also revealed a discrepancy between attitudes and practices towards food hygiene. There is an immediate need for continuous training among food handlers regarding safe food handling practices.     

Graph-based multilevel temporal video segmentation

This paper presents a graph-based multilevel temporal video segmentation method. In each level of the segmentation, a weighted undirected graph structure is implemented. The graph is partitioned into clusters which represent the segments of a video. Three low-level features are used in the calculation of temporal segments’ similarities: visual content, motion content and shot duration. Our strength factor approach contributes to the results by improving the efficiency of the proposed method. Experiments show that the proposed video scene detection method gives promising results in order to organize videos without human intervention.     

Is it PAO-GAO competition or metabolic shift in EBPR system? Evidence from an experimental study

Reduced EBPR performance in full and bench-scale EBPR studies was linked to the proliferation of GAOs but often time with the lack of any evidence. In this study, a detailed enzymatic study was coupled with batch tests and electron microscopy results for a realistic explanation. The results eliminated the possibility of population shift from PAO to GAO or other non-PAO due to the short batch test period provided which would not allow a population shift and further justified with the electron microscopy results. The results indicate that glycogen serves not only as source of reducing power for PHA production but also serves as an alternative energy source when the poly-P pool of the PAOs is depleted. Slow generation of ATP via glycolytic pathway at 5 degrees C cannot satisfy energy requirements of EBPR cells to complete several cell functions including acetate uptake and PHA storage. However, the glycolytic pathway is efficiently operable at warm temperatures (> 20 degrees C). The reduced performance of enhanced EBPR facilities operated at warm temperature may not be a result of GAO proliferation; instead it may be related the efficient use of the glycolytic pathway by PAOs which results in more glycogen storage and less P uptake, thereby reducing the EBPR performance.     

Treatment of olive mill wastewater by different physicochemical methods and utilization of their liquid effluents for biological hydrogen production

In this study various two-stage processes were investigated for biological hydrogen production from olive mill wastewater (OMW) by Rhodobacter sphaeroides O.U.001. Two-stage processes consist of physicochemical pretreatment of OMW followed by photofermentation for hydrogen production. Explored pretreatment methods were chemical oxidation with ozone and Fenton's reagent, photodegradation by UV radiation, and adsorption with clay or zeolite. Among these different two-stage processes, strong chemical oxidants like ozone and Fenton's reagent have the highest color removal (90%). However, their effluents were observed to be unsuitable for both hydrogen production and bacterial growth. On the other hand, clay treatment method was selected as the optimum process that allows fast and low-cost treatment as well as its effluent found to have the highest hydrogen production potential (31.5 m³ m^?3). Spent-clay regeneration was also investigated on the grounds that solid waste minimization is important for the overall efficiency of this process.