Essential oils of aromatic plants with insecticidal properties are nowadays considered as alternative insecticides to protect cultures from attack by insect pest. The aims of the present work were to evaluate the toxicity of the essential oils vapors of two aromatic plants (Lippia multiflora Mold. and Aframomum latifolium K. Schum) against Bemisia tabaci and to characterize their chemical composition. The highest fumigant toxicity against B. tabaci adults was observed with the L. multiflora oil: by exposure to 0.4 microL/L air, the lethal time inducing 90% mortality (LT90) was below 2 hours for this essential oil whereas it reached 15 h in the case of the A. latifolium oil. Both oils were analyzed by GC-FID and GC-MS on two capillary columns. The oil of L. multiflora contained a majority of oxygenated terpenoids mainly represented by the two acyclic components linalool (46.6%) and (E)-nerolidol (16.5%); the oil of A. latifolium was dominated by hydrocarbonated terpenoids among them beta-pinene (51.6%) and beta-caryophyllene (12.3%) were the two major components. 相似文献
Summary The first-order degradation kinetics of bisphenol A diglycidyl ether (BADGE; CAS No. 1675-54-3) has been studied in three water-based food simulants (3% (W/V) acetic acid, distilled water and 15% (V/V) ethanol) at various temperatures. BADGE and its first and second hydrolysis products were determined by reversed-phase high-performance liquid chromatography with fluorescence detection. Nonlinear regression was used to fit the experimental data at 40, 50 and 60°C with the proposed kinetic equations; Arrhenius' equation was then fitted to the rate constants obtained and the kinetic models were tested by comparing experimental data obtained at 70°C with the kinetic curves calculated using the rate constants predicted for this temperature. The half-life of BADGE was longest in ethanol and shortest in acetic acid. The rings opening in acetic acid appears to happen by means of active hydrogens whereas in the other simulants it is mainly influenced by the formation of acid/base adducts. The results imply that resins which comply with existing legislation on the migration of unreacted monomer may still contaminate foodstuffs. 相似文献
A reactivity study of the most important elementary steps (propagation, intermolecular degradative transfer, and re‐initiation) in free‐radical polymerization of acrylfuranic systems, furfuryl acrylate (FA), and furfuryl methacrylate (FM), using the frontier molecular orbital theory is described. A qualitative explanation of reactivity trends of these steps for both systems is given based on absolute values of the SOMO/HOMO gap. The small difference between values of kp for FA and FM compared to that found for MA and MMA ( ) is justified semi‐quantitatively by applying a formulation for the change of energy in the transition state using second‐order perturbation theory.
Er3+–Yb3+ co‐doped Lu3Ga5O12 nanogarnets were prepared and characterized; their structural and luminescence properties were determined as a function of the Yb3+ concentration. The morphology of the nanogarnets was studied by HRTEM. Under 488 nm excitation, the nanogarnets emit green, red, and near‐infrared light. The decay curves for the (4S3/2, 2H11/2) and 4F9/2 levels of the Er3+ions exhibit a non‐exponential nature under resonant laser excitation and their effective lifetimes are found to decrease with an increase in the Yb3+ concentration from 1.0 to 10.0 mol %. The non‐exponential decay curves are well fitted to the Inokuti–Hirayama model for S=8, indicating that the mechanism of interaction for energy transfer between the optically active ions is of dipole–quadrupole type. Upon 976 nm laser excitation, an intense green upconverted emission is clearly observed by the naked eyes. A significant enhancement of the red‐to‐green intensity ratio of Er3+ ions was observed with an increase in Yb3+ concentration. The power dependence and the dynamics of the upconverted emission confirm the existence of two‐photon upconversion processes for the green and red emissions. 相似文献
Antimicrobial agents have a major practical importance in food, pharmaceutical and cosmetic applications for preventing contamination. Our group has developed a novel class of cationic diacyl glycerol arginine-based surfactants denoted 1414RAc and 1212RAc. To assess the antimicrobial properties of these new surfactants we have studied how they interact with 1,2-dipalmitoyl-sn-glycero-3-phosphocoline (DPPC) and 1,2-dimiristoyl-sn-glycero-3-phosphocoline (DMPC) as model membranes, as well with living organisms endowed or not with external barriers, such as gram negative bacteria, the human protozoa Leishmania and mammalian cell line.
The structure and phase characteristics of mixed monolayers have been assessed through the analysis of static elasticity. The extent of component miscibility of surfactant and phospholipid in mixed monolayers has been studied using the additivity rule and the excess free energy of a mixture as a function of the phospholipid molar fraction for different surface pressure values. In all the mixtures studied, the mixed monolayer is thermodynamically favoured except for the 1212RAc/DMPC case that exhibits positive values of excess free energy.
The interaction with living cells has cytotoxic effects only in eukaryotic cells, by unspecific membrane permeabilization. 相似文献
We describe the synthesis, characterization by IR and electronic spectra, magnetic susceptibility measurements, analytical data, kinetic study by differential‐scanning calorimetry, and thermogravimetric analysis of the thermal decomposition under N2 of the adducts 2 – 7 with pyridine or substituted pyridines of bis(piperidine‐1‐carbodithioato‐κS,κS′)di‐μ‐thioxodithioxoditungsten(V) ( 1 ), to which the general formula [W2B2(pipCS2)2S2(μ‐S)2] is assigned (pipCS2=piperidine‐1‐carbodithioato and B=pyridine (py), 3‐methylpyridine (3‐Mepy), 4‐methylpyridine (4‐Mepy), 3,5‐dimethylpyridine (3,5‐Me2py), pyridin‐3‐amine (3‐pyNH2), and pyridin‐4‐amine (4‐pyNH2)). For the endothermic process of loss of the coordinated base B, we calculated activation energies with a method reported previously by us; the mechanism and pre‐exponential Arrhenius factor of this reaction were also determined. A relationship between the pyridines' basicity, IR and electronic spectral data, and activation energies was established. 相似文献
Orange peel by-products generated in the food industry are an important source of value-added compounds that can be potentially reused. In the current research, the effect of oven-drying (50–70 °C) and freeze-drying on the bioactive compounds and antioxidant potential from Navelina, Salustriana, and Sanguina peel waste was investigated using pressurized extraction (ASE). Sixty volatile components were identified by ASE-GC-MS. The levels of terpene derivatives (sesquitenenes, alcohols, aldehydes, hydrocarbons, and esters) remained practically unaffected among fresh and freeze-dried orange peels, whereas drying at 70 °C caused significative decreases in Navelina, Salustriana, and Sanguina peels. Hesperidin and narirutin were the main flavonoids quantified by HPLC-MS. Freeze-dried Sanguina peels showed the highest levels of total-polyphenols (113.3 mg GAE·g−1), total flavonoids (39.0 mg QE·g−1), outstanding values of hesperedin (187.6 µg·g−1), phenol acids (16.54 mg·g−1 DW), and the greatest antioxidant values (DPPH•, FRAP, and ABTS•+ assays) in comparison with oven-dried samples and the other varieties. Nanotechnology approaches allowed the formulation of antioxidant-loaded nanoemulsions, stabilized with lecithin, starting from orange peel extracts. Those provided 70–80% of protection against oxidative UV-radiation, also decreasing the ROS levels into the Caco-2 cells. Overall, pressurized extracts from freeze-drying orange peel can be considered a good source of natural antioxidants that could be exploited in food applications for the development of new products of commercial interest. 相似文献
Air monitoring networks are necessary to assess air quality in order to reduce pollution to levels which minimize harmful effects on human health and the environment. This paper describes a method to design or optimize air quality monitoring networks for nitrogen dioxide and ozone and its application in Malaga, a medium large city located in Andalusia, southern Spain, with traffic being the main source of air pollution. The completion of this method revealed that the old assessment network in Malaga was badly designed and made it possible to determine that one traffic-orientated and one background control station were necessary for NO2 assessment in Malaga, as well as two control stations for O3. First the number of stations necessary is obtained from historical data. Sampling campaigns with passive diffusion samplers at 74 sites were then carried out to obtain information on the pollution distribution in Malaga. The average concentrations found for NO2 and O3 were 22.8 μg/m3 and 64.3 μg/m3 respectively. Maximum values of up to 42.2 μg/m3 NO2 were found in Malaga city centre and O3 reached 91.5 μg/m3 downwind from the emission source. After spatial interpolation of the obtained values with Geographical Information Systems, a selection of the best locations for the monitoring stations was made, in line with the macro- and microscale siting requirements of the European Directive 2008/50/EC on ambient air quality and cleaner air for Europe. 相似文献
The extract of Cardiospermum halicacabum L. (C. halicacabum) obtained from flower, leaf and vine was loaded into modified phospholipid vesicles aiming at obtaining sprayable, biocompatible and effective nasal spray formulations for the treatment of nasopharyngeal diseases. Penetration enhancer-containing vesicles (PEVs) and hyalurosomes were formulated, and stabilized by adding a commercial gelatin from fish (20 mg/mL) or chondroitin sulfate from catshark cartilages (Scyliorhinus canicula, 20 mg/mL). Cryo-TEM images confirmed the formation of spherical vesicles, while photon correlation spectroscopy analysis disclosed the formation of small and negatively-charged vesicles. PEVs were the smaller vesicles (~100 nm) along with gelatin-hyalurosomes (~120 nm), while chondroitin-PEVs and chondroitin-hyalurosomes were larger (~160 nm). Dispersions prepared with chondroitin sulfate were more homogeneous, as the polydispersity index was ~0.15. The in vitro analysis of the droplet size distribution, average velocity module and spray cone angle suggested a good spray-ability and deposition of formulations in the nasal cavity, as the mean diameter of the droplets was in the range recommended by the Food and Drug Administration for nasal targets. The spray plume analysis confirmed the ability of PEVs, gelatin-PEVs, hyalurosomes and gelatin-hyalurosomes to be atomized in fine droplets homogenously distributed in a full cone plume, with an angle ranging from 25 to 30°. Moreover, vesicles were highly biocompatible and capable of protecting the epithelial cells against oxidative damage, thus preventing the inflammatory state. 相似文献