Structural information from progression bands in the FTIR spectra of long chain n-alkanes

The low temperature FTIR spectrum of long chain n-alkanes has been investigated in the region between the C-C stretching and CH₂ twisting fundamentals (1050-1133 cm⁻¹). With successive annealing and cooling stages, extended chain crystals of n-C₁₉₈H₃₉₈ show an improvement in the regularity of the progression bands observed. This is related to a ‘perfecting’ of the crystals. A once-folded sample of the same alkane shows additional features between 1050 and 1100 cm⁻¹, attributed to resonance modes from a tight (110) fold. These disappear on transformation to the extended form, to be replaced by progression bands. Assignment of the individual bands enables the length of the all-trans chain to be estimated and this method is used to show that centre-branched long chain n-alkanes have a folded conformation. It is also shown that the chain length derived from such FTIR data for a 1:1 molar mixture of n-C₁₆₂H₃₂₆ and n-C₂₄₆H₄₉₄ is consistent with a triple layer superlattice structure.     

Voltammetric response of ferrocene-grafted mesoporous silica

The electrochemical behavior of ferrocene moieties immobilized by covalent grafting on ordered mesoporous silica samples has been studied by cyclic voltammetry in aqueous medium using carbon paste electrodes modified with these solids. The functionalized silica samples were obtained using (3-(ferrocenylamide)propyl)triethoxysilane as the grafting agent. The results have been discussed in relation to the ferrocene content in the materials and compared to those obtained with non-ordered ferrocene-grafted silica gels. Well-defined voltammetric signals have been observed in spite of the insulating character of the mesoporous silica matrix and they were found to increase as a function of the ferrocene groups content in the material. They displayed a better stability upon continuous cycling potentials in comparison to those recorded with amorphous gels, suggesting a beneficial effect of the long-range structural order on the electron transfer processes in such confined media.     

Sub-dominant bacteria as keystone species in microbial communities producing bio-hydrogen

Nowadays mixed cultures are considered as a serious alternative to pure cultures in biotechnological processes. Mixed cultures can use various organic substrates and be operated under unsterile and continuous conditions. Although most of studies dealing with fermentative hydrogen production have focused on dominant species, sub-dominant bacteria can also have a significant effect despite their low abundance. The determination of their exact ecological role is essential for better understanding microbial metabolic networks in mixed cultures.     

面向新兴市场的电动助力转向系统

过去的几年中,EPS作为传统液压系统的替代产品已经进入汽车制造领域.与先前的预测相反,EPS不仅适用于小型汽车,而且某些12V中型汽车(例如大众帕萨特)也适于安装电动系统.     

Integrated Fault Detection and Isolation: Application to a Winery's Wastewater Treatment Plant

In this paper, an integrated object-oriented fuzzy logic fault detection and isolation (FDI) module for a biological wastewater treatment process is presented. The defined FDI strategy and the software implementation are detailed. Using experimental results obtained with a one cubic meter fixed bed reactor for the anaerobic digestion of industrial wine distillery vinasses, examples of material and biological failures are presented together with the corresponding fault signals generated by the FDI module.     

The formation of halogen-specific TOX from chlorination and chloramination of natural organic matter isolates

The formation of disinfection by-products (DBPs) is a public health concern. An important way to evaluate the presence of DBPs is in terms of the total organic halogen (TOX), which can be further specified into total organic chlorine (TOCl), bromine (TOBr), and iodine (TOI). The formation and distribution of halogen-specific TOX during chlorination and chloramination of natural organic matter (NOM) isolates in the presence of bromide and iodide ions were studied. As expected, chloramination produced significantly less TOX than chlorination. TOCl was the dominant species formed in both chlorination and chloramination. TOI was always produced in chloramination, but not in chlorination when high chlorine dose was used, due to the limited presence of HOI in chlorination as a result of the oxidation of iodide to iodate in the presence of excess chlorine. The formation of TOI during chloramination increased as the initial iodide ion concentration increased, with a maximum of ∼60% of the initial iodide ion becoming incorporated into NOM. Iodine incorporation in NOM was consistently higher than bromine incorporation, demonstrating that the competitive reactions between bromine and iodine species in chloramination favoured the formation of HOI and thus TOI, rather than TOBr. Correlations between the aromatic character of the NOM isolates (SUVA₂₅₄ and % aromatic C) and the concentrations of overall TOX and halogen-specific TOX in chloramination were observed. This indicates that the aromatic moieties in NOM, as indicated by SUVA₂₅₄ and % aromatic C, play an important role in the formation of overall TOX and halogen-specific TOX in chloramination. THMs comprised only a fraction of TOX, up to 7% in chloramination and up to 47% in chlorination. Although chloramine produces less TOX than chlorine, it formed proportionally more non-THM DBPs than chlorine. These non-THM DBPs are mostly unknown, corresponding to unknown health risks. Considering the higher potential for formation of iodinated DBPs and unknown DBPs associated with the use of chloramine, water utilities need to carefully balance the risks and benefits of using chloramine as an alternative disinfectant to chlorine in order to satisfy guideline values for THMs.