Crude Oil Model Emulsion Characterised by means of Near Infrared Spectroscopy and Multivariate Techniques

Water-in-oil emulsions are investigated by means of multivariate analysis of near infrared (NIR) spectroscopic profiles in the range 1100 — 2250 nm. The oil phase is a paraffin-diluted crude oil from the Norwegian Continental Shelf. The influence of water absorption and light scattering of the water droplets are shown to be strong. Despite the strong influence of the water phase, the NIR technique is still capable of predicting the composition of the investigated oil phase.     

Impact of formic/acetic acid and ammonia pre-treatments on chemical structure and physico-chemical properties of Miscanthus x giganteus lignins

Miscanthus x giganteus was treated with formic acid/acetic acid/water (30/50/20 v/v) for 3 h at 107 °C and 80 °C, and soaking in aqueous ammonia (25% w/w) for 6 h at 60 °C. The effects of these fractionation processes on chemical structure, physico-chemical properties and antioxidant activity of extracted lignins were investigated. Lignins were characterized by their purity, carbohydrate composition, thermal stability, molecular weight and by Fourier transform infrared (FTIR), 1H and quantitative 13C nuclear magnetic resonance (NMR), adiabatic broadband {13C-1H} 2D heteronuclear (multiplicity edited) single quantum coherence (g-HSQCAD). The radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl (DPPH) was also investigated. Formic/acetic acid pretreatment performed in milder conditions (80 °C for 3 h) gave a delignification percentage of 44.7% and soaking in aqueous ammonia 36.3%.Formic/acetic acid pretreatment performed in harsh conditions (107 °C for 3 h) was more effective for extensive delignification (86.5%) and delivered the most pure lignin (80%). The three lignin fractions contained carbohydrate in different extent: 3% for the lignin obtained after the formic/acetic acid pretreatment performed at 107 °C (FAL-107), 5.8% for the formic/acetic acid performed at 80 °C (FAL-80) and 13.7% for the ammonia lignin (AL). The acid pretreatment in harsh conditions (FAL-107) resulted in cleavage of β-O-4′ bonds and aromatic C-C. Repolymerisation was thought to originate from formation of new aromatic C-O linkages. Under milder conditions (FAL-80) less β-O-4′ linkages were broken and repolymerisation took place to a lesser extent. Ammonia lignin was not degraded to a significant extent and resulted in the highest weight average 3140 g mol⁻¹. Despite the fact of FAL-107 repolymerisation, significant phenolic hydroxyls remained free, explaining the greater antioxidant activity.     

Corrosion behaviour of steel in concentrated phosphoric acid solutions

The corrosion rates of steel in concentrated phosphoric acid (1.0-11.0 M) were determined by the weight loss method, at three temperatures 298, 308 and 323 K. Results obtained show that corrosion rate increases with both acid concentration and temperature. The logarithm of corrosion rate was fitted against the acid concentration, values of Hammett H_o and Strehlow R_o(H) functions. The activation energies, enthalpies and entropies of the dissolution process were determined.     

Waste mixture composition by thermogravimetric analysis

In this work thermogravimetric analysis is applied to examine pyrolysis of single waste components and their blends in order to determine the composition of an unknown waste mixture. The superposition property is assumed, i.e. the mixture thermal degradation curve is obtained as the sum of the curves corresponding to its constituents. The results show that if blended, the individual components are more clearly recognised from the differential mass loss curves. This allows a better identification of the composition. Inaccuracy in determining the composition increases if interactions occur between components, which is the case for PVC-newspaper blend. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reactivity of [HC{(C(Me)N(Dipp))}2Ca{N(SiMe3)2}(THF)] (Dipp = C6H3Pr2-2,6) with C-H acids: Synthesis of heteroleptic calcium η-organometallics

A series of heteroleptic calcium η⁵-C₅R₅ cyclopentadienides supported by an N-Dipp (Dipp = 2,6-ⁱPr₂C₆H₃)-substituted β-diketiminate ligand have been synthesised by selective protonolysis of the readily available reagent [HC{(C(Me)N(Dipp))}₂Ca{N(SiMe₃)₂}(THF)] with tetramethylcyclopentadiene, fluorene, indene or cyclopentadiene. No reaction was observed with pentamethylcyclopentadiene, presumably for steric reasons. The tetramethylcyclopentadienyl, fluorenyl and indenyl compounds were characterised by variable temperature ¹H NMR and X-ray crystallography. Each complex was found to exist as a mononuclear species both in solution and in the solid state and to be highly sterically crowded, as evidenced by the variable temperature NMR studies. DFT (B3LYP/LANL2DZ) calculations on the model complexes [CaH(C₅Me₄H)], [CaH(C₁₃H₉)] and [CaH(C₉H₇)] indicate that the precise structures of such heteroleptic compounds are a result of both stereoelectronic and steric influences. Attempts to isolate the unsubstituted cyclopentadienyl were unsuccessful, but resulted in the crystallographic analysis of the dimeric calcium siloxide [HC{(C(Me)N(Dipp))}₂Ca(μ-OSiMe₃)]₂.     

Characterisation of RPLC columns packed with porous sub-2 microm particles

Eight commercially available sub-2 microm octadecyl silane columns (C18 columns) have been characterised by the Tanaka protocol. The columns can be grouped into two groups that display large differences in selectivity and peak shape due to differences in hydrophobicity, degree of surface coverage and silanol activity. Measurements of particle size distributions were made using automated microscopy and electrical sensing zone measurements. Only a weak correlation could be found between efficiency and particle size. Large differences in column backpressure were observed. These differences are not related to particle size distribution. A more likely explanation is differences in packing density. In order to take full advantage of 100-150 mm columns packed with sub-2 microm particles, it is often necessary to employ not only an elevated pressure but also an elevated temperature. A comparison between columns packed with sub-2, 3 and 5 microm versions of the same packing indicates potential method transferability problems for several of the columns due to selectivity differences. Currently, the best alternative for fast high-resolution LC is the use of sub-2 microm particles in combination with elevated pressure and temperature. However, as shown in this study additional efforts are needed to improve transferability as well as column performance.     

Assessment of nanoparticle loading and dispersion in polymeric materials using optical coherence tomography

The inclusion of small concentrations of nanoparticles can significantly enhance the thermal and electrical properties, and to a lesser degree the mechanical performance, of polymers. Dispersion of nanoparticles during mixing is problematic, with poor mixing resulting in particle agglomeration (i.e. particle clustering), which subsequently limits the potential for property enhancement. Achieving good dispersion is considered key to large-scale production and commercialization of polymer nanocomposites (PNCs), and a measurement technique capable of quantitatively characterizing particle loading and dispersion would significantly enhance product development. This paper presents the results of a study using a static light scattering technique, Fourier domain optical coherence tomography (FD-OCT), for discriminating between different particle loadings and levels of dispersion. The technique has been applied to a range of PNCs including epoxy resins reinforced with nanoclay platelets, silica microspheres or multi-walled carbon nanotubes (MWCNTs), and zinc oxide and lithium aluminate reinforced polypropylene.     

Enantioselective behaviour of ethylated γ-cyclodextrins as GC stationary phases for chlorinated pesticides and phase characterisation by HPLC

Summary Small composition changes can influence the enantiomeric selectivity of alkylated cyclodextrins used as stationary phase in high resolution gas chromatography. A method is presented for the characterisation of such cyclodextrins using high performance liquid chromatography combined with evaporative light scattering and mass spectrometric detection (atmospheric pressure chemical ionisation in the positive ion mode). The method was applied to different batches of octakis (2,3,6-tri-O-ethyl)-γ-cyclodextrins (TEG-CD). Some showed a very good enantiomer selectivity for chlorinated pesticides. Separation evaluations were carried out with an improved test mixture containing selected, partly enantiomer enriched pesticides. Capillaries based on underethylated TEG-CD with up to 4 free OH groups dissolved in OV 1701-OH allowed the separation of α-HCH, o,p’-DDT, compounds of technical chlordane (cis-and trans-chlordane, U82, MC5, MC7, MC8) as well as chlordane metabolites (cis- and trans-heptachlor epoxide, oxychlordane) into enantiomers.     

Development and optimization of a novel genetic algorithm for identifying nanoclusters from scanning transmission electron microscopy images

Whilst technological advancements have allowed imaging at atomic resolution using scanning transmission electron microscopy (STEM), identification of nanocluster structures has proven difficult due to their low thermal stability, and often resultant low-symmetry. In this work, we look at a novel solution to this problem using a genetic algorithm (GA). GAs are search methods for the minimization of statistical problems based on natural evolution. We develop a STEM model first described by Curley et al. (2007) and, using high-symmetry cluster structures as test subjects, look at the effectiveness and efficiency of the GA at optimizing orientation parameters for a cluster when compared to a model solution. We find for a 309-atom icosahedron that a random minimizing search would prove more efficient than a GA; however, for a 309-atom decahedron the GA becomes more effective and efficient than a random search. We predict that as we continue to lower symmetry of our test cases, we will find the GA becomes even more efficient at optimizing this otherwise computationally expensive problem.     

Cohomological characterisation of monads

Let X be an n‐dimensional smooth projective variety with an n‐block collection , with , of coherent sheaves on X that generate the bounded derived category . We give a cohomological characterisation of torsion‐free sheaves on X that are the cohomology of monads of the form where . We apply the result to get a cohomological characterisation when X is the projective space, the smooth hyperquadric or the Fano threefold V₅. We construct a family of monads on a Segre variety and apply our main result to this family.