Potential for reducing emissions in a diesel engine by fuelling with conventional biodiesel and Fischer-Tropsch diesel

A gas-to-liquid (GTL) fuel derived from Low Temperature Fischer-Tropsch process has been tested in an automotive diesel engine fulfilling Euro 4 emissions regulations. Both regulated and non-regulated emissions have been compared with those of a commercial diesel fuel, a commercial biodiesel fuel and a GTL-biodiesel fuel (30% and 70% v/v, respectively) in order to check blending properties, synergistic effects and compatibility between first and second generation production technologies for biofuel consumption in current diesel engines. After presenting a detailed literature review, and confirming that similar efficiencies are attained with the four tested fuels under identical road-like operating conditions (this meaning fuel consumption is inversely proportional to their heating values), significant reductions in smoke opacity, particulate matter emissions and particle number concentration were observed with both GTL and biodiesel fuels, with small changes in NO_x emissions. Compared with the reductions in PM emissions derived from the use of biodiesel fuels, those derived from using GTL fuels were quite similar, despite its lower soot emissions reductions. This can be explained by the lower volatile organic fraction of the PM in the case of GTL. By adequately blending both fuels, a considerable potential to optimise the engine emissions trade-off is foreseen.     

Finding an internal state of RC4 stream cipher

The RC4 is a stream cipher widely deployed in software applications due to its simplicity and efficiency. The paper presents a cryptanalytic attack that employs the tree representation of this cipher and introduces an abstraction in the form of general conditions for managing the information about its internal state. In order to find the initial state, the tree of general conditions is searched applying the hill-climbing strategy. The complexity of this attack is lower than that of an exhaustive search. The attack is derived from a general cryptanalytic approach for a class of table-shuffling ciphers, whose next-state function permutes the table entries. Incorporating the general conditions in the existing backtracking algorithm, the estimated complexity of the cryptanalytic attack is decreased below the best published result but the RC4 still remains a quite secure cipher in practice.     

Doping of lanthanum cobaltite by Mn: thermal,magnetic, and catalytic effect

Great differences in crystallographic phases, magnetic properties, and catalytic activity were detected in lanthanum cobaltite and cobaltite modified with the insertion of 10 wt.% of Mn. Atomic absorption spectroscopy, BET area measurements, XRD analysis, TPR, and FT-IR suggest that the total insertion of manganese in the LaCoO₃ structure is successful. Thermal stability is reached for LaCo_0.90Mn_0.10O₃ up to 973 K without loss of the perovskite structure. The magnetic properties of the as-grown compounds are maintained after a first reduction process up to 723–773 K, while presence of segregated phases is observed after reduction at 973 K. The catalytic activity evaluated in the total combustion of acetyl acetate shows a decrease in the ignition temperature, i.e. an increase in the catalytic activity for the LaCo_0.90Mn_0.10O₃ perovskite. A significant enhancement in the catalytic activity expressed as intrinsic activity, mol m⁻² h⁻¹, with the manganese substitution was found.     

Tunable resonance transmission modes in hybrid heterostructures based on porous silicon

ABSTRACT: In this work, we report the experimental results and theoretical analysis of strong localization of resonance transmission modes generated by hybrid periodic/quasiperiodic heterostructures (HHs) based on Porous Silicon (PSi). The HHs are formed by stacking a quasiperiodic Fibonacci (FN) substructure between two Distributed Bragg Reflectors (DBRs). FN substructure defines the number of strong localized modes that can be tunable at any given wavelength and be unfolded when a partial periodicity condition is imposed. These structures show interesting properties for biomaterials research, biosensor applications and basic studies of adsorption of organic molecules. We also demonstrate the sensitivity of HHs to material infiltration.     

Synthesis and characterization of styrene‐butyl acrylate polymers,varying feed composition in a semicontinuous emulsion process

Two‐stage polymerization has been used to improve properties of two‐component polymers. In this work, a semicontinuous emulsion process varying feed composition along the reaction is used to produce copolymer chains of different composition as conversion proceeds. Polymer composition and evidence of branching were determined by ¹H‐NMR. Polymer molecular weight values determined by GPC are beyond the range where mechanical properties depend on molecular weight. Mechanodynamic properties show a copolymer type behavior with a synergistic effect around the 50/50 styrene/butyl acrylate composition ratio. For such composition, mechanical performance superiority of variable composition copolymer with respect to two‐stage polymer was confirmed with stress–strain tests carried out at several temperatures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3964–3971, 2007     

Acrylic-phosphate glasses composites as self-curing controlled delivery systems of antibiotics

New antibiotic delivery systems based on self-hardening methyl methacrylate (MMA)/polymethyl methacrylate (PMMA) systems and phosphate glasses (PG) in the system P₂O₅–CaO–Na₂O have been developed. Self-curing formulations were prepared by mixing the solid component containing PMMA beads, different proportions of PG (30–70 wt %) and vancomycin (5 wt %) as antibiotic, with the liquid component made of MMA monomer. Dough and setting times increased with the content of PG but peak temperature decreased to values well below to guarantee the chemical stability of the antibiotic drug, gentamicin or vancomycin. Mechanical properties of the PMMA/PG composites were evaluated in compression test giving rise to values of compressive strength in the range of 100 MPa. The release of vancomycin was analyzed in vitro by immersion of samples in phosphate buffer of pH=7.4. Release profiles were influenced by the content of PG present in the cement. An initial burst of drug release was observed in all cases. The composites with 70 wt % PG released nearly the total amount of drug loaded in a period of 45 days, and those containing 60 wt % PG released the 70% of the vancomycin in the same period of time. However, either the control of the composite with 30 wt % PG released only the 30% of the drug in 10–15 days. The surface of the drug-loaded composites before and after release experiments was analyzed by ESEM. The deposition of some aggregates at certain points of the surface was detected for the specimens immersed in buffer phosphate after 45 days. This material was characterized by FTIR and Raman spectroscopy as an amorphous phosphate formed by calcium ortho and pyrophosphates, and indicates an interaction between the hydrated layer at the place of the glass and the surrounding medium.     

Correlation of HPLC and AOAC Methods to Assess the All-trans-Lutein Content in Marigold Flowers

A reversed-phase C₃₀ high-performance liquid chromatography (HPLC) method was used to separate the lutein isomers of marigold flowers. The pigments were extracted from marigold meal by an Association of Official Analytical Chemists (AOAC) modified method. The unsaponified extract showed the presence of several lutein ester isomers and after saponification four major lutein isomers were detected. The relationship between all- trans -lutein, assessed by HPLC, and total xanthophylls, assessed by AOAC, was determined. A regression equation, with a high correlation coefficient ( r ² =0·972), which allows for the calculation of all- trans -lutein from total xanthophylls content is proposed.     

Application of the technique of environmental scanning electron microscopy to the paper industry

The environmental scanning electron microscope was used in conjunction with a heating stage to study in situ the polymerization process in the manufacturing of filter papers for the automotive industry. The images obtained from the video recording were converted into TIFF format with a computer program and were then analyzed using an image analyzer to assess the percentage shrinkage during the cure process. These experiments yield valuable information that is impossible to obtain with other electron microscopy techniques, for example, determining whether the polymer envelops the fibers or not, or whether there is a greater or lesser degree of anchoring between fibers.     

Isolation and Partial Characterization of Okenia (Okenia hypogaea) Starch

Okenia hypogaea (Schlech. & Cham.) belongs to the family of the Nyctaginacea, which produces a seed that is composed mainly of starch, the probable origin of Okenia hypogaea is Mexico. The aim of this work was to isolate the starch from Okenia hypogaea and to evaluate its chemical composition, along with some physicochemical and functional properties. Okenia gave a starch yield of 36 %; this starch had an amylose content of 26.1 %, with a fat content similar to corn starch, but with a higher ash fraction. Okenia starch possessed a small granule size (1—3 μm), the same as amaranth starch, with similar characteristics of stability and clarity of pastes as corn starch. At 60 °C the water retention capacity of okenia starch was higher than that of corn starch, but at higher temperatures an inverse pattern was found. When the temperature in the experiments increased, solubility and swelling values increased; okenia starch had higher swelling values than corn starch over the range of temperatures assayed. Okenia starch also presented a lower freeze‐thaw stability than corn starch on the first two cycles. Overall, it was concluded that due to its physicochemical and functional properties, it is worthwhile to test the use of okenia starch in the cosmetic and food industry.