Hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization

The aim of this study was to improve hybrid dual-curable cyanate ester/boron phosphate composites via sequential thiol-ene photopolymerization and thermal polymerization for high performance applications such as aerospace and electronic devices. A novel 2,2′-diallylbisphenol A dicyanate ester (DA-BADCy) which is the allyl group containing cyanate ester was synthesized and characterized. DA-BADCy, silicon containing monofunctional thiol compound, trifunctional thiol compound and boron phosphate were cured using both ultraviolet (UV) and thermal methods. Using thiol-ene system, cyanate ester formulations, which are normally prepared at high temperatures, were prepared at room temperature. This study maintains ease of application for cyanate esters. Thermal stability, flammability and thermal conductivity of the samples were evaluated by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI) and laser flash method, respectively. The samples were characterized with the following analysis; gel content, water absorption capacity and stress–strain test. Hydrophobicity of the samples was determined by the contact angle measurements. Moreover, the surface morphology of the samples was investigated by a scanning electron microscopy (SEM–EDS). The obtained results prove that the composites have good thermal and mechanical properties and with the help of easier preparation techniques, they can be used in many applications such as aerospace, electronic devices, materials engineering.     

Nitrification of fertilizer wastewaters in a biofilm reactor

The nitrification characteristics of fertilizer wastes were investigated in a biofilm system using a submerged aerated filter. The attachment of biomass on packing media was studied. Supplement of organic carbon in the form of glucose and yeast extract enhanced biofilm formation although the nitrifiers did not require organic carbon for growth. After an attachment period, continuous operation of the reactor at different loading rates and dissolved oxygen levels was investigated. The maximum achievable nitrification rate was strongly dependent on the dissolved oxygen. In the dissolved oxygen range of 3·2–3·5 mg dm⁻³, the maximum ammonia removal rate was about 0·17 kg NH₄ N m⁻³ day⁻¹. When the dissolved oxygen was increased to 4·9 mg dm⁻³, removal rates as high as 0·41 kg NH₄ N m⁻³ day⁻¹ could be obtained. Nitrite accumulation depended on the bulk nitrogen and dissolved oxygen concentrations.     

硅业副产物四氯化硅在离子液体中溶解—-电沉积的研究

研究多晶硅工业的主要副产品四氯化硅(SiCl_4)在离子液体中的溶解、电沉积过程。结果表明,SiCl_4在离子液体中的溶解度随温度升高而降低,离子液体的导电率随温度升高而增加。在阴离子为[TNf_2]的情况下,阳离子为[N_(1114)]的季铵盐类离子液体比咪唑类[Bmim]离子液体具有更好的SiCl_4溶解度和导电性。SiCl_4在季铵盐类离子液体的溶解度随烷基主链长度增加而增大,随侧链长度增加而降低。[N_(1114)][TNf_2]和SiCl_4之间形成C-Cl、Si-O和C-Si键,在[N_(1114)][TNf_2]-SiCl_4体系中S_i~(4+)的还原电位为-2.2V。在温度25℃、SiCl_4浓度0.3mol/L、电流密度20A/m~2、电解时间2h的条件下可电沉积得到较为致密的硅薄膜,呈球形颗粒状分布。     

Laccases and Tyrosinases in Organic Synthesis

Laccases (Lac) and tyrosinases (TYR) are mild oxidants with a great potential in research and industry. In this work, we review recent advances in their use in organic synthesis. We summarize recent examples of Lac-catalyzed oxidation, homocoupling and heterocoupling, and TYR-catalyzed ortho-hydroxylation of phenols. We highlight the combination of Lac and TYR with other enzymes or chemical catalysts. We also point out the biological and pharmaceutical potential of the products, such as dimers of piceid, lignols, isorhamnetin, rutin, caffeic acid, 4-hydroxychalcones, thiols, hybrid antibiotics, benzimidazoles, benzothiazoles, pyrimidine derivatives, hydroxytyrosols, alkylcatechols, halocatechols, or dihydrocaffeoyl esters, etc. These products include radical scavengers; antibacterial, antiviral, and antitumor compounds; and building blocks for bioactive compounds and drugs. We summarize the available enzyme sources and discuss the scalability of their use in organic synthesis. In conclusion, we assume that the intensive use of laccases and tyrosinases in organic synthesis will yield new bioactive compounds and, in the long-term, reduce the environmental impact of industrial organic chemistry.     

Engineered Glycosidases for the Synthesis of Analogs of Human Milk Oligosaccharides

Enzymatic synthesis is an elegant biocompatible approach to complex compounds such as human milk oligosaccharides (HMOs). These compounds are vital for healthy neonatal development with a positive impact on the immune system. Although HMOs may be prepared by glycosyltransferases, this pathway is often complicated by the high price of sugar nucleotides, stringent substrate specificity, and low enzyme stability. Engineered glycosidases (EC 3.2.1) represent a good synthetic alternative, especially if variations in the substrate structure are desired. Site-directed mutagenesis can improve the synthetic process with higher yields and/or increased reaction selectivity. So far, the synthesis of human milk oligosaccharides by glycosidases has mostly been limited to analytical reactions with mass spectrometry detection. The present work reveals the potential of a library of engineered glycosidases in the preparative synthesis of three tetrasaccharides derived from lacto-N-tetraose (Galβ4GlcNAcβ3Galβ4Glc), employing sequential cascade reactions catalyzed by β3-N-acetylhexosaminidase BbhI from Bifidobacterium bifidum, β4-galactosidase BgaD-B from Bacillus circulans, β4-N-acetylgalactosaminidase from Talaromyces flavus, and β3-galactosynthase BgaC from B. circulans. The reaction products were isolated and structurally characterized. This work expands the insight into the multi-step catalysis by glycosidases and shows the path to modified derivatives of complex carbohydrates that cannot be prepared by standard glycosyltransferase methods.     

Utilization of Whey and Grape Must for Citric Acid Production by Two Yarrowia lipolytica Strains

In this study, utilization of whey and grape must were investigated for citric acid production using Yarrowia lipolytica NBRC 1658 and a domestic strain Y. lipolytica 57. In addition to its use as a sole nutrient source, whey was also fortified with glucose or fructose as well as other nutrients. The best results for citric acid production were obtained in the medium containing whey supplemented with fructose. Maximum citric acid concentrations in this medium were 49.23 and 32.65 g/L for the domestic and NBRC 1658 strains, respectively. In grape must, maximum citric acid concentrations obtained using domestic and NBRC 1658 strains were 32.09 and 10.39 g/L, respectively. Both of the natural nutrient sources were found to be promising for utilization in citric acid production process. A domestic Turkish yeast strain was confirmed to be superior for citric acid production for the first time. This can be targeted for enhancing citric acid production efficiencies from locally available substrates such as whey or grape must.     

Preparation of comb‐type grafted hydrogels composed of polyacrylamide and chitosan and their use for DNA adsorption

Comb‐type grafted hydrogels composed of polyacrylamide (PAAm) and chitosan (CT) were prepared and used for DNA adsorption. Instead of direct grafting of the acrylamide monomer onto the CT chain, semitelechelic PAAm with carboxylic acid end groups (PAAm–COOH) was synthesized by free‐radical polymerization with mercaptoacetic acid as the chain‐transfer agent, and it was grafted onto CT with amino groups. The synthesis of telechelic PAAm–COOH and the formation of comb‐type grafted hydrogels were confirmed by attenuated total reflectance/Fourier transform infrared spectroscopy and scanning electron microscopy measurements. The prepared comb‐type grafted hydrogels were used as sorbents in DNA adsorption experiments conducted at +4°C in a tris(hydroxymethyl)aminomethane/ethylenediaminetetraacetic acid solution of pH 7.4. DNA adsorption capacities as high as 2.0 × 10³ μg of DNA/g of dry gel could be achieved by the comb‐type hydrogels with higher PAAm contents. This value was approximately 6 times higher than that of CT alone. In addition, the comb‐type hydrogels showed a high adsorption/desorption rate depending on the PAAm content in the hydrogel. As a result, these comb‐type hydrogels carrying higher amounts of DNA may be considered good candidates for achieving higher removal rates for anti‐DNA antibodies and for effective gene therapy systems. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Performance Assessment of a Potato Crisp Frying Process

Frying is a common and popular cooking method, which has been widely used in food manufacturing, though it is a very energy-intensive process. Energy analysis has been commonly used to assess the performance of fryers. In this study, we attempted to exergetically assess the performance of a potato crisp frying system, which consists of three main components, a combustor, a heat exchanger, and a fryer. In the analysis, we utilized the actual operational data obtained from the literature. We determined exergy destruction in each system component and the whole system. We calculated universal and functional exergy efficiency values for the system components and compared them with each other. We also undertook a parametric study to investigate how the overall cycle performance was affected by changing the reference environment temperature and some operating conditions. We illustrated the exergy results through the Grassmann (exergy loss and flow) diagram. We calculated the universal exergetic efficiency values of 58, 82, and 77% for the combustor, heat exchanger, and fryer, respectively, with a universal exergetic efficiency value of 4% for the whole frying system. We found that the fryer had the highest functional exergetic efficiency value of 74%, followed by the heat exchanger with 47% and the combustor with 0.08%.     

Torque and bending moment acting on a flexible shaft agitated by disk turbines in a gas–liquid stirred vessel

The torque and bending moment acting on a flexible overhung shaft in a gas–liquid stirred vessel agitated by a Rushton turbine and three different curved-blade disk turbines(half circular blades disk turbine, half elliptical blades disk turbine, and parabolic blades disk turbine) were experimentally measured by a customized moment sensor. The results show that the amplitude distribution of torque can be fitted by a symmetric bimodal distribution for disk turbines, and generally the distribution is more dispersive as the blade curvature or the gas flow rate increases. The amplitude distribution of shaft bending moment can be fitted by an asymmetric Weibull distribution for disk turbines. The relative shaft bending moment manifests a "rising-falling-rising" trend over the gas flow number, which is a corporate contribution of the unstable gas–liquid flow around the impeller, the gas cavities behind the blades, and the direct impact of gas on the impeller. And the "falling" stage is greater and lasts wider over the gas flow number for Rushton turbine than for the curved-blade disk turbines.     

Cephalaria syriaca seed oil

Cephalaria syriaca shrad., in Turkish pelemir, grows predominantly in the southeastern district of Turkey as a weed in cereal fields. Pelemir seeds are sometimes used for extraction of their oil, as an improver of baking value of wheat, and as an antistaling agent for bread. The seeds contain 7.8% moisture; their chemical composition on a dry basis is: crude fat, 25.3%, crude protein, 15.9%; N-free extract, 40.4%; crude fiber, 11.9%; crude ash, 6.5%. Characteristics of the seed oil are: specific gravity at 25 C, 0.9229; refractive index at 25 C, 1.4706; saponification value, 192; iodine value, 88.4; thiocyanogen value, 58.8; Reichert-Meissl value, 0.36; Polenske value, 0.25; unsaponifiable matter, 1.24%; hydroxyl value, 20.9. The fatty acid components are: lauric acid, 1.5%; myristic acid, 19.5%; palmitic acid, 9.4%; stearic acid, 2%; oleic acid, 23.0%; linoleic acid, 36.9%. The chemical composition of extracted cakes on a dry basis is: crude protein, 20.4%; crude fat, 0.8%; N-free extract, 50.5%; crude ash, 6.4%; crude fiber; 14.4%%; saponin, 7.5%. The oil contains 7.8% epoxy acid, calculated as epoxy oleic acid, which makes its use as an edible oil rather difficult but renders it usable in industries using epoxidized oils. Due to its high content of myristic acid, the oil is very suitable for soapmaking as well.