HYDROCRACKING OF ARABIAN MIX ASPHALTENES IN THE PRESENCE OF MODIFIED RED MUD

ABSTRACT

Asphaltenes precipitated from an Arabian Mix vacuum residue were hydro-cracked in a batch autoclave at 435 and 460°C for 5-90 min. Experiments without catalyst, with modified red mud and with an industrial Co Mo/Al₂0₃ catalyst were compared. The products were fractionated into gas, naphtha, oil, asphaltenes and coke. Feed asphaltenes and several product fractions were characterised by elemental analysis, by average molecular mass and by ¹H n.mr. Due to the hydrogenation activity, both catalysts caused - with similar efficiency - the decrease of coke formation and the increase of quantity and quality of oil.     

Limited angle STIM and PIXE tomography of single cells

STIM (scanning transmission ion microscopy) tomography has been shown to be a valuable method for the three-dimensional characterization of microsamples. It has, however, rarely been employed for the study of single cells, since a free-standing sample is needed for an ordinary tomography experiment. This requirement places high demands on sample preparation techniques.In this study cells fixated on a substrate rather than free-standing were used for tomography. Since the substrate prevented a full rotation of the sample an algorithm for limited-angle tomography was devised. STIM projections covering only a limited angular range of ca. 120° were supplemented with simulated projections generated from a back and forth iteration between real space and Radon space. The energy loss caused by the substrate was subtracted from each projection. The cells were reconstructed using filtered backprojection. The surface of the cells as well as some interior structures could be reconstructed.Following the STIM projections a lesser number of PIXE (particle induced X-ray emission) projections were taken in order to obtain information about the elemental distribution of the sample. From the PIXE projections the three-dimensional phosphorus distribution within the cell was reconstructed using limited-angle tomography. Superimposition of the STIM and PIXE tomograms revealed the location of intracellular structures.Whereas STIM tomography is sensitive to density contrast, which are greatest at the surface, PIXE tomography is sensitive to changes in elemental concentration. Hence, the combination of the two methods can be very fruitful, while the limited angle approach can compensate some of the difficulties associated with tomography of single cells, namely preparation difficulties and excessive sample damage.     

STUDY OF THE TEMPERATURE AND ENTHALPY OF THERMALLY INDUCED PHASE-TRANSITIONS IN n-ALKANES, THEIR MIXTURES AND FISCHER-TROPSCH WAXES

A precise determination of the temperatures and enthalpies of thermally induced various phases of n-alkanes, especially those having the molecular weights in the petroleum wax range, have been done by using a differential scanning calorimeter (DSC). These phase transitional parameters are shown to be dependent on the rate of heating/cooling, particularly on the faster rates. Also, the parameters measured during heating cycle (melting) differ from those obtained during the cooling cycle (crystallization). The typical shape of the solid-solid transition curve in the DSC thermograms(cooling cycle) of even n-alkanes readily distinguishes these from the odd n-alkanes, which is greately influenced by the increase in the carbon numbers in the chain (n-C₃₄ and beyond) and the purity of the sample.High molecular weight n-alkanes also showed instability in the structures at the phase transitions

The formation of solid solutions of n-alkanes have been studied by measuring phase transitional parameters and studying nature of the DSC thermograms of various binary and multicomponent mixtures of n-tetracosane (n-C₂₄) with other n-alkanes. It is observed that the immiscibility between two n-alkanes of the binary mixture begins when chain-length difference between them is more than four carbon atoms. In between the two extremes of solid solution and eutectic formations, there also existed the partial miscibility of two n-alkanes, particularly at high temperatures

The DSC thermograms of multicomponent n-alkane mixtures and Fischer-Tropsch waxes revealed that perfect solid solution is formed when the involved n-alkanes have carbon number very close to each other or the carbon number distribution is in a narrow range with smaller chain n-alkanes dominating.     

High pressure/temperature treatments to inactivate highly infectious prion subpopulations

High hydrostatic pressure can be used for gentle pasteurization of food as well as a physical parameter to study the stability and energetics of biomolecules. High pressure has been recently postulated as a feasible technology to decontaminate scrapie infectious materials. Here we discuss the kinetic parameters driving the inactivation of the Transmissible Spongiform Encephalopathy agents and the perspectives of pressure as a thermodynamic parameter to obtain a deeper insight into the aggregation of the 263K strain of scrapie. At 60–80 °C an efficient pressure inactivation of infectious scrapie prions was observed during short pressure treatments at 800 MPa (3 × 5 min cycles). However, discrepancies between in vivo infectivity counts and the results of an enzyme immunoassay further revealed that the infectivity was inactivated faster and much more efficiently than PrP^res was degraded, indicating that pressure affects a highly infectious subpopulation of scrapie prions.

Industrial relevance

Conventional inactivation methods for the agents of the Transmissible Spongiform Encephalopathies are not compatible with food processing due to the required aggressive conditions. High pressure assisted thermal sterilization methods are nowadays attracting attention as a food preservation technology able to preserve quality attributes. Here the stark effects in the secondary prion structure of high pressure combined with heat below the usual denaturing conditions were investigated with specific tests. This technology was proven to be a feasible alternative to achieve the decontamination of TSE risk materials at milder conditions. Kinetic data provided here should be useful to establish criteria to inactivate prions under pressure.     

RHEOLOGY, PARTICLE SIZE DISTRIBUTION, AND ASPHALTENE DEPOSITION OF VISCOUS ASPHALTIC CRUDE OIL-IN-WATER EMULSIONS FOR PIPELINE TRANSPORTATION

The rheology of an asphaltic heavy crude oil-in-water emulsions stabilized by an anionic (RN) and a nonionic (TEP) surfactants individually or in a mixture has been studied. The investigated crude oil has a non-Newtonian, time dependent, shear thickening, rheopectic behavior with a relatively high yield stress. The relatively high yield stress of this crude oil is attributed to the presence of a relatively high asphaltene and resins content. The viscosity ofhe crude oil decreases when it is emulsified with synthetic formation water in the form of an oil-in-water type of emulsion using a nonionic or an anionic surfactant. It has been found that, the maximum oil content required for forming an oil-in-water emulsion of acceptable viscosity is the 60% oil-containing emulsion. However, the 70% oil-containing emulsion is not an oil-in-water type of emulsion but it is rather a complicated mixture of oil-in-water-in-oil type of emulsion. The presence of the anionic and the nonionic surfactants together has a synergistic effect in decreasing the total surfactant concentration required to stabilize the emulsion and to form low viscosity emulsion. It has been emphasized that the nonionic surfactant has a positive contribution in forming emulsions with low viscosity. Meanwhile, the anionic surfactant contributes in stabilizing the emulsion at lower concentrations. Flocculation point measurements showed that the added surfactants caused no sign of asphaltene deposition. This implies that it is safe to use the investigated surfactants in forming oil-in-water emulsion for viscous asphaltic crude oils without any fear of asphaltene deposition.     

Root signals of rank order processors

A rank order processor (ROP) is a signal processor that operates purely by making rank determination on input values, and includes as special cases `median filters' and `rank order filters'. It is shown how the methods of automata theory can be used to show the existence of root signal (i.e., fixed point) sets of input sequences, and to determine them for specific ROPs, in either algebraic or graphical form. Observations on graph/subgraph relationships are made. It is shown how certain earlier methods of determining root signals can be improved and extended to the general case. Remarks on the synthesis problem are made     

On Darwinian Networks

We suggest Darwinian Networks (DNs) as a simplification of working with Bayesian networks (BNs). DNs adapt a handful of well‐known concepts in biology into a single framework that is surprisingly simple yet remarkably robust. With respect to modeling, on one hand, DNs not only represent BNs but also faithfully represent the testing of independencies in a more straightforward fashion. On the other hand, with respect to three exact inference algorithms in BNs, DNs simplify each of them while unifying all of them. DNs can determine good elimination orderings using the same platform as used for modeling and inference. Finally, we demonstrate how DNs can represent two additional frameworks. Practical benefits of DNs include faster algorithms for inference and modeling.     

Bemessungskonzept für fußgängerinduzierte Brückenschwingungen

Design concept for the analysis of pedestrian‐induced bridge vibration. Unexpected vibrations of footbridges, e.g. during inauguration of Millennium Bridge in London and Passerelle Solferino in Paris, have drawn engineers' attention to more accurate forecast models to determine pedestrian‐induced vibrations and especially pedestrian‐structure‐interaction of light and slightly damped footbridges in the design phase. This contribution presents a programme to simulate bridge vibrations with realistic ‘numerical pedestrians’, which is calibrated against measured response under real pedestrian loading. By means of this simulation tool observed vibrations and pedestrian‐structure‐interaction phenomena can be analysed. In a second step an engineering model based on a spectral approach is derived, which enables to determine characteristic pedestrian‐induced structural response. Hence, if necessary the design of the footbridge can be adjusted or damping measures can be planned to fulfill serviceability requirements. A design concept for the dynamic analysis of the reversible serviceability limit state, which fulfills the Eurocode requirements, is described and an innovative consideration and definition of comfort criteria are proposed.     

MicroRNA Profiling in Oesophageal Adenocarcinoma Cell Lines and Patient Serum Samples Reveals a Role for miR-451a in Radiation Resistance

Many patients with Oesophageal Adenocarcinoma (OAC) do not benefit from chemoradiotherapy treatment due to therapy resistance. To better understand the mechanisms involved in resistance and to find potential biomarkers, we investigated the association of microRNAs, which regulate gene expression, with the response to individual treatments, focusing on radiation. Intrinsic radiation resistance and chemotherapy drug resistance were assessed in eight OAC cell lines, and miRNA expression profiling was performed via TaqMan OpenArray qPCR. miRNAs discovered were either uniquely associated with resistance to radiation, cisplatin, or 5-FU, or were common to two or all three of the treatments. Target mRNA pathway analyses indicated several potential mechanisms of treatment resistance. miRNAs associated with the in vitro treatment responses were then investigated for association with pathologic response to neoadjuvant chemoradiotherapy (nCRT) in pre-treatment serums of patients with OAC. miR-451a was associated uniquely with resistance to radiation treatment in the cell lines, and with the response to nCRT in patient serums. Inhibition of miR-451a in the radiation resistant OAC cell line OE19 increased radiosensitivity (Survival Fraction 73% vs. 87%, p = 0.0003), and altered RNA expression. Pathway analysis of effected small non-coding RNAs and corresponding mRNA targets suggest potential mechanisms of radiation resistance in OAC.