Nucleation and growth of carbon black particles during thermal decomposition of benzene

The authors determined the mechanism of carbon black formation during the thermal decomposition of benzene diluted with a stream of nitrogen. The kinetics study of nucleation and growth of particles led them to the following conclusions: The initial hydrocarbon is transformed by a gas phase reaction into macromolecules. The partial pressure of the macromolecules increases with reaction time until a supersaturation is high enough to induce condensation of macromolecules into droplets. The formation of liquid nuclei eliminates the supersaturation, and the formation of additional liquid nuclei becomes impossible. The macromolecules which continue to be formed maintain the nuclei growth. The liquid droplets are pyrolysed into a solid material. A statistical study of the distribution curves of the particle diameters indicates that the growth rate of each particle is proportional to its diameter.     

Chamomile extraction with supercritical carbon dioxide: Mathematical modeling and optimization

Supercritical fluid extraction of chamomile using carbon dioxide was investigated in the current study. A model that accounts for both particle and fluid phase was presented for the supercritical extraction. The distribution coefficient of chamomile extract, between solid and solvent has been determined using genetic algorithm method. The model was solved numerically and was successfully validated with experimental data. The model was found to give superior results when compared to experimental data. The effect of particle diameter on extraction yield was investigated using the proposed model. Using genetic algorithm optimization technique 313.15 K and 20 MPa were found as the optimum temperature and pressure, respectively.     

Synthesis Method for Thiosulfonate and Report of Its Insecticidal Activity in Anagasta kuehniella (Lepidoptera: Pyralidae)

Insect pests have caused economic losses valued at billions of dollars in agricultural production. Anagasta kuehniella (Zeller), the Mediterranean flour moth, is of major economic importance as a flour and grain feeder and is often a severe pest in flourmills. This study provides a suitable route for the direct preparation of thiosulfonates 2 and 3 from thiols, under mild conditions, with good yields; these thiosulfonates were tested for their regulatory effect on insect growth. The chronic ingestion of thiosulfonates resulted in a significant reduction in larval survival and weight. In addition, the tryptic activity of larvae was sensitive to these thiosulfonates. Results suggest that thiosulfonates 2 and 3 have a potential antimetabolic effect when ingested by A. kuehniella. The use of AgNO₃/BF₃·OEt₂ and Al(H₂PO₄)₃/HNO₃ provides a suitable route for the direct preparation of thiosulfonates from thiols under mild conditions with good yields. These thiosulfonates were toxic for A. kuehniella larvae, suggesting their potential as biotechnological tools.     

SHRINKAGE OF DATES (Phoenix Dactilyfera L.) DURING DRYING

In this paper the shrinkage of Dates (Phoenix dactilyfera L.) during drying was observed. Samples were dried in a convective tray dryer under three different conditions (60°C-11.1%RH, 70°C-7.2%RH and 80°C-4.7%RH) and three different air velocities (0.5m/s, l.0m/s and 1.5m/s). Sample shrinkage was directly (using a caliper) and indirectly measured (snapshot area measured). The indirect manner shows a higher precision. The geometry applied in the shrinkage solution proved that the ellipsoidal geometry of the dates, may be successfully approached to a cylinder. Three mathematical models developed by Suzuki et al. (1976) were applied to correlate the dates surface to its moisture content. The core model presented the best fit to the experimental data.     

Nb2O5 as efficient and recyclable photocatalyst for indigo carmine degradation

Heterogeneous photocatalysis is a significant green technology for application in water purification. The application of Nb₂O₅ catalyst for the photodegradation of contaminants is few reported in the literature. Thus, the Nb₂O₅ catalyst was characterized by SEM, FTIR, surface area and charge surface density. This catalyst was applied to degrade indigo carmine dye, which was compared with degradation catalyzed by TiO₂ and ZnO. Almost 100% of dye degradation occurred at 20, 45 and 90 min for TiO₂, ZnO and Nb₂O₅, respectively. The effect of Nb₂O₅ catalyst concentration, pH and ionic strength (μ) was investigated. The Nb₂O₅ activity increased at 0.7 g/L and for higher catalyst concentrations the degradation was kept constant. Degradation of indigo carmine dye catalyzed by Nb₂O₅ was improved at pH < 4.0 and μ = 0.05 mol/L. TiO₂, ZnO and Nb₂O₅ were recovered and re-applied in other nine reaction cycles. While TiO₂ and ZnO have an abrupt loss of their catalytic activity, Nb₂O₅ maintained 85% of catalytic activity after 10 reaction cycles.     

Quantification of chicory root bitterness by an ELISA for 11β,13-dihydrolactucin

Chicory root (Cichorium intybus L. var. sativum) is an important foodstuff appreciated for its bitter taste, which is caused by sesquiterpene lactones. These compounds represent a quality parameter for monitoring the raw material. Using polyclonal antibodies, an enzyme-linked immunosorbent assay (ELISA) was developed to quantify the bitter compound 11β,13-dihydrolactucin in chicory root. Assay linearity ranged from 4.6 to 300 ng/ml, with intra- and inter-assay variations of 4.9% and 7.2%, respectively. An IC₅₀ of 2 ng/ml and a detection limit of 0.16 ng/ml were obtained. No or little cross-reactions with other sesquiterpene lactones occurred. Roots of three different chicory varieties were evaluated for their bitter taste and were investigated by the ELISA. Distinct concentrations of 11β,13-dihydrolactucin ranging from 485 to 1720 mg/kg dry matter were correlated with the bitterness degree (r = 0.9). The ELISA appeared sensitive, selective, accurate and may serve as screening tool in breeding of chicory roots for bitterness.     

Evaluation of three-dimensional and two-dimensional full displacement fields of a single edge notch fracture mechanics specimen, in light of experimental data using X-ray tomography

The aim of this study is to show the validity of a 3D numerical approach and the 2D theoretical approaches from 3D experimental results on a single edge notch cracked specimen loaded in mode I. The three displacement components all over the volume were measured by means of Digital Volume Correlation coupled with X-ray computed tomography. The numerical approach and the experimental one give similar results with differences equivalent to the accuracy of the method of measurements. The theoretical approach provides higher results and is not relevant to experimental results, but this approach allows an evaluation of the 3D effect zone.     

Thermogravimetric study of thermal decontamination of soils polluted by hexachlorobenzene, 4-chlorobiphenyl, naphthalene, or n-decane.

To determine decontamination behavior as affected by temperature, shallow beds of a clay-rich, a calcerous, and a sedimentary soil, artificially polluted with hexachlorobenzene, 4-chlorobiphenyl, naphthalene, or n-decane, were separately heated at 5 degrees C min-1 in a thermogravimetric analyzer. Temperatures for deep cleaning of the calcerous and the sedimentary soil increased with increasing boiling point (bp) of the aromatic contaminants, but removal efficiencies still approached 100% well below the bp. Decontamination rates were therefore modelled according to a pollutant evaporation-diffusion transport model. For the calcerous and sedimentary soils, this model reasonably correlated removal of roughly the first 2/3 of the naphthalene, but gave only fair predictions for hexachlorobenzene and 4-chlorobiphenyl. It was necessary to heat the clay soil above the aromatics bp to achieve high decontamination efficiencies. Weight loss data imply that for temperatures from near ambient to as much as 150 degrees C, interactions of each aromatic with the clay soil, or its decomposition products, result in lower net volatilization of the contaminated vs. neat clay. A similar effect was observed in heating calcerous soil polluted with hexachlorobenzene from near ambient to about 140 degrees C. Decontamination mechanisms remain to be established, although the higher temperatures needed to remove aromatics from the clay may reflect a more prominent role for surface desorption than evaporation. This would be consistent with our estimates that the clay can accommodate all of the initial pollutant loadings within a single surface monolayer, whereas the calcerous and sedimentary soils cannot.     

Organic–inorganic hybrid materials derived from epoxy resin and polysiloxanes: Synthesis and characterization

In this study, hybrid materials based on epoxy resin were prepared as transparent self‐supported films by a sol–gel process. 4,4′‐Diaminodiphenylmethane or oligomeric epoxy resin were used as precursors, which were conveniently functionalized with trialkoxysilanes as end‐groups. The effect of the introduction of poly (dimethylsiloxane) was also investigated. The hybrid films showed good thermal stability, a nondefined glass transition temperature, and a dense morphology without phase segregation. The tendency to a flat surface could be observed by atomic force microscopy. The hybrid films also showed good performance as coatings for glass plates, with an improved hydrophobic character in comparison to neat epoxy resin. POLYM. ENG. SCI., 48:141–148, 2008. © 2007 Society of Plastics Engineers