Intrinsic affinity of acid-activated bentonite towards hydrogen and carbon dioxide

The effect of acid activation on bentonite affinity toward carbon dioxide (CO₂) and hydrogen (H₂) was investigated at ambient conditions. Characterization through X-ray diffraction and fluorescence, thermal gravimetric analysis, nitrogen adsorption-desorption isotherms, Fourier Transform Infrared spectroscopy and differential scanning calorimetry allowed correlating newly induced textural and structural features with adsorptive properties. Optimum acid treatment improved the specific surface area and porosity. The resulting decrease in dehydration temperature indicates decay in hydrophilic character. The affinity improvement towards hydrogen was due to Brønsted acidity suppression and surface basicity attenuation, which are essential requirements for adsorption on aluminosilicates (AS) via weak Lewis Acid-Base interactions, but excessive acid attack was detrimental. Low Si/Al surfaces should be suitable for CO₂ capture, while moderately acid-treated clays should be interesting candidates as hydrogen adsorbents. This allows envisaging promising prospects for low-cost AS-based materials intended for selective CO₂-free capture and storage of hydrogen without energy and safety constraints.     

The food preservative potential of essential oils: is lemongrass the answer?

Several essential oils of medicinal plants possess proven antimicrobial activity and are suitable for applications on the food industry. The oil from Cymbopogon citratus (lemongrass) has been reported to have a wide range of biological activities. However, there are few controlled studies confirming its antimicrobial activity. The aim of our study was to assess the antimicrobial potential of lemongrass oil against a wide spectrum of food spoilage and pathogenic bacteria and yeast in liquid and vapour phase. The chemical composition of the oil was analyzed by gas chromatography; 14 components were identified and geranial (28.93 %), neral (24.30 %) and myrcene (23.92 %) were the most abundant constituents. Lemongrass oil showed potent antimicrobial activity against Gram positive bacteria and exhibited the strongest antifungal effect against Candida albicans and C. parapsilosis. Minimum inhibitory concentration varied from 0.019 to 1.25 mg mL^?1 for Gram positive bacteria and yeasts, indicating Staphylococcus aureus, S. epidermidis and C. albicans as the most susceptible strains. Moreover, the diameter of inhibition zone (DIZ) increased with increasing essential oil (EO) volume. Considerably superior antimicrobial activity was observed in the vapour phase. The DIZ resulting from the exposure to EO vapour was significantly larger than that from the same volume in the liquid phase. The DIZ varied from 22 to 90 mm for Candida strains. There is growing evidence that EO in vapour phase are effective antimicrobial systems and that they do have advantages over the use of oil in liquid phase. Our results imply that lemongrass oil could be useful for the development of novel types of natural preservatives for food control.     

Adaptive high-order sliding mode control based on quasi-time delay estimation for uncertain robot manipulator

This paper presents the design, and validation of a new adaptive control system based on quasi-time delay estimation (Q-TDE) augmented with new integral second-order terminal sliding mode control (ISOTSMC) for a manipulator robot with unknown dynamic uncertainty and disturbances. Contrary to the conventional TDE, the proposed Q-TDE becomes sufficient to invoke a fixed artificial time delay and utilize the past data only of the control input to approximate the unknown system''s dynamic uncertainties. The incorporating of new adaptive reaching law with ISOTSMC augmented with Q-TDE policy ensures the continuous performance tracking of the robot manipulator''s trajectories using output feedback. This combination may achieve high performance with a significant chattering reducing procedure. By utilizing the Lyapunov function theory, it can be demonstrated that the robot system is stable and all signals in closed-loop are converging in finite time. Consequently, Simulation and comparative studies with two degrees of freedom robot manipulator were carried out to validate the effectiveness of the designed control scheme.     

A robust and secure key-frames based video watermarking system using chaotic encryption

Multimedia Tools and Applications - Currently we are facing a wide interest in multimedia security and copyright protection due to the explosion of data exchange in the Internet and the extensive...     

Insight into Factors Influencing Wound Healing Using Phosphorylated Cellulose-Filled-Chitosan Nanocomposite Films

Marine polysaccharides are believed to be promising wound-dressing nanomaterials because of their biocompatibility, antibacterial and hemostatic activity, and ability to easily shape into transparent films, hydrogels, and porous foams that can provide a moist micro-environment and adsorb exudates. Current efforts are firmly focused on the preparation of novel polysaccharide-derived nanomaterials functionalized with chemical objects to meet the mechanical and biological requirements of ideal wound healing systems. In this contribution, we investigated the characteristics of six different cellulose-filled chitosan transparent films as potential factors that could help to accelerate wound healing. Both microcrystalline and nano-sized cellulose, as well as native and phosphorylated cellulose, were used as fillers to simultaneously elucidate the roles of size and functionalization. The assessment of their influences on hemostatic properties indicated that the tested nanocomposites shorten clotting times by affecting both the extrinsic and intrinsic pathways of the blood coagulation system. We also showed that all biocomposites have antioxidant capacity. Moreover, the cytotoxicity and genotoxicity of the materials against two cell lines, human BJ fibroblasts and human KERTr keratinocytes, was investigated. The nature of the cellulose used as a filler was found to influence their cytotoxicity at a relatively low level. Potential mechanisms of cytotoxicity were also investigated; only one (phosphorylated microcellulose-filled chitosan films) of the compounds tested produced reactive oxygen species (ROS) to a small extent, and some films reduced the level of ROS, probably due to their antioxidant properties. The transmembrane mitochondrial potential was very slightly lowered. These biocompatible films showed no genotoxicity, and very importantly for wound healing, most of them significantly accelerated migration of both fibroblasts and keratinocytes.     

Double perovskite oxides Sr2MMoO6 (M = Fe and Co) as cathode materials for oxygen reduction in alkaline medium

The oxygen reduction reaction (ORR) was studied on Sr₂MMoO₆ (M = Fe and Co) double perovskites, prepared by a solid-state reaction, in 0.5 M NaOH at 25 °C with a rotating disk electrode (RDE). The two oxide powders were characterized by X-ray diffraction, scanning electron microscopy and BET analysis. The electrochemical techniques considered are linear voltammetry, steady state polarization and ac impedance spectroscopy. The electrocatalysts (SFMO/C, SCMO/C) consisting of the double perovskite oxides and carbon (Vulcan XC-72) were mixed and spread out into a thin layer on a glassy carbon substrate. At room temperature, a significantly electrocatalytic activity is observed for both electrocatalysts. Compared to SFMO/C, the SCMO/C electrocatalyst was found to show a relatively high electrocatalytic activity for O₂ reduction, which agrees well with the results obtained using the ac impedance spectroscopy.     

IDMA Based Anti-collision in RFID Networks

Even though object identification is its main objective, it is generally accepted that there are some technological challenges that should be addressed in order to exploit the full potential of RFID (Radio frequency identification). The anti-collision problem is one of them. Despite the different proposed methods, it still needs further study on how to improve identification ability. This paper presents a novel algorithm with IDMA (Interleave division multiple access) scheme to resolve the anti-collision problem for RFID. IDMA, which is one of the most promising technologies for high data rate wireless systems, can be regarded as a special case of CDMA (Code division multiple access). In contrast to CDMA, which separates tags by signatures or spreading codes, distinct interleavers are the only means to separate tags for IDMA. In this paper, a RFID based IDMA receiver is proposed and compared to classical systems. Simulation results demonstrate that this system provides an improvement in performance in terms of bit error rate in dense scenarios (large number of tags) and it offers an efficient alternative to systems with classical spreading sequence.     

Comprehensive modeling of mat density effect on duckweed (Lemna minor) growth under controlled eutrophication

The effect of mat density on duckweed (Lemna minor) growth was studied under controlled conditions: 12.5h a day light exposure and 342 mol m(-2) s(-1) light intensity at 20 degrees C. The plant growth was carried out in Hoagland medium for 7 days without harvesting. The results revealed a maximal biomass growth rate of 88 g-dry m(-2) (1,470 g-wet m(-2)) at an optimal initial mat density of 45 g-dry m(-2) (750 g-wet m(-2)), with removal rates for nitrogen (N) and phosphorus (P) of 483 mg-Nm(-2) d(-1) and 128 mg-Pm(-2) d(-1), respectively. A mathematical model that takes into account the mat density was developed in order to simulate the growth of Lemna minor under controlled eutrophication. Based on experiments carried out, the model exhibits a reliability of 89% . The model remains to be validated at the full-scale level.