Experimental Study and Modeling of Essential Oil Extraction from Plants by Hydrodistillation

Hydrodistillation of essential oils from leaves of myrtle, rosemary, and sour orange was experimentally studied and the extraction process was modeled. A mass balance was carried out over an assumed flat leave particle and the use of Fick's second law of diffusion led to the mass transfer equation. Its resolution required adequate boundary and initial conditions. The model considered the effect of the main processing parameters on the overall essential oil extraction efficiency as well as the determination of the optimum conditions. To assess the reliability of the model, yield curves for all studied conditions and variation of the oil composition with time were compared with the experimentally obtained results for each plant leave. The agreement seems to be reasonable, although some refining of the model is necessary by taking into account both the diffusion and reaction contributions.     

The Relative Importance of Usability and Functionality Factors for E‐Health Web Sites

With the growing usage of the Internet, the demand for online health care information and advice as well as the number of health‐related Web sites are increasing. In case of online health information and advice, the user interface replaces face‐to‐face communication. To ensure that the users' needs are met, it is critical to balance functionality and usability in the design of the Web site. The present study seeks to identify the complex interrelationships among the various factors of usability and functionality concerning e‐health Web sites. Two Turkish e‐health Web sites were assessed for evaluation in this study. The findings show that the users of the health information Web sites give a higher priority to functionality and its factors, whereby the highest relative importance is on “services/facilities” and “personalization/categorization of information.” The most important usability factors related to the e‐health Web sites are “memorability” and “interaction.” © 2012 Wiley Periodicals, Inc.     

Effect of the acid-activated clays on the properties of porous clay heterostructures

Porous clay heterostructures (PCHs) are quite a new class of solid acids, and exhibited pore sizes in the rarely observed supermicropore to small mesopore region. They are formed by the surfactant-directed assembly of mesostructured silica within the two dimensional galleries of smectite layered silicates. The acid activation of the smectite clay was an effective way to improve the acidity and the mesoporosity of the raw clay mineral. We have studied the effect of the type of clay minerals on the properties of porous acid-activated clay heterostructures (PACHs). Three different raw clays with different cation exchange capacities were selected and acid-activated at an acid/clay ratio of 0.2 (w/w). The synthesis of PACHs was achieved and characterized by powder x-ray diffraction, nitrogen adsorption-desorption and acidity using cyclohexylamine as probe molecule. A short order in the structure, as revealed by the powder x-ray diffraction of PACH materials was observed, with higher surface areas, pore volumes and acidity for some clays. These properties were not enhanced as we expected, and compared to the PCHs, indicating that the origin or type of clay affects the final properties of the derived materials. By using a soft extraction of the surfactants via chemical way, the stability and the properties of PCH and PACH materials were not improved except for one type of clay.     

Hydrothermal processing of amorphous hydrous zirconia gels in the presence of 1,12-diaminododecane

In the presence of 1,12-diaminododecane (DADD), tetragonal ZrO₂ nanoparticles (ca. 10 nm) with high phase purity (monoclinic volume content: less than 0.1) and large surface area (100 m²/g) and pure monoclinic ZrO₂ nanorods (aspect ratio of ca. 10) have been successfully prepared upon hydrothermal processing at 230 °C for 3 days of zirconyl nitrate-derived hydrous zirconia gels at different pH values. The complementary data from FTIR, Raman, TGA/DTG confirm the presence of hydrocarbon fragments (1-3 wt%) on the surface of DADD-derived zirconia nanocrystals. These organic residues account for their features in the phase composition, particle size and morphology, and surface wettability.     

Monitoring of theophylline dehydration in a vacuum contact dryer by near-infrared spectroscopy

This study is a contribution for development of in-line monitoring of solid-state forms during pharmaceuticals manufacturing. It concerns the dehydration behaviour of theophylline monohydrate by stirred bed vacuum contact drying. First it was demonstrated that NIRS coupled with PLS regression enabled to measure in-line and in situ the exact composition of the mixture of different forms of theophylline (and water) during drying. Second, the influence of operating parameters (temperature and water activity) on the kinetics of solid state transformations was investigated. It was shown that the dehydration advanced first by the formation of the metastable anhydrate and after a lag time of the stable one. Once the stable appeared, formation of the metastable form came to an end. The temperature was found out to be the main factor controlling the overall process rate but also the final contents of the stable and metastable anhydrates for the considered dryer and operating conditions range.     

Inverse method for the dynamical analysis of wall shear rates using three-segment probes in parallel plate rheometer

Mass transfer measurements were conducted on a Parallel Plate Rheometer (PPR) using the limiting diffusion current method, i.e. the polarography technique. The database constructed was exploited for the validation of the inverse method under a well-controlled unsteady shear flow. This method is based on a numerical sequential estimation. It has been applied to determine of the wall shear rate in the upper disk of the PPR. It requires the numerical inversion of the convection diffusion equation in order to apply it to instantaneous mass transfer measurements. This requires the use of electrochemical probe, which allows the determination of the local mass transfer rate for known flow kinematics. A multi-segment electrochemical probe has been used. The directional characteristics of the three-segment probe were highlighted. The directional angle effect and the frequencies of oscillations effect were studied in order to test the robustness of the inverse method within the presence of such factors. The obtained results demonstrate that the inverse method allows a good determination of the shear rate, which follows the experimental one for different cases tested in a satisfactory way.     

Biocompatible nanofilm coating by magneto-luminous polymerization of methane

Coating is uniquely feasible means to impart biocompatibility to artificial materials to be used in biology and medicine, because a totally different surface-state could be created. However, it is necessary to understand factors that control “biocompatibility” first. The examination of molecular level factors involved in interfacial interaction revealed that the best surface-state for biocompatibility should contain no chemical functional group. Such a surface-state cannot be created by conventional chemical means, and application of conventional coating could be used in rather limited cases only. Magneto-luminous polymerization of methane yields nanofilm of amorphous carbon, which seems to be the closest to the ideal non-interacting surface. Fundamental factors involved in interactions of polymer surface with surrounding medium, and mechanisms how magneto-luminous polymerization coating yields amorphous carbon nanofilm, which has the least interfacial interaction capability, are described in this paper.