Identification of onosma visianii roots extract and purified shikonin derivatives as potential acaricidal agents against tetranychus urticae

There is an increasing need for the discovery of reliable and eco-friendly pesticides and natural plant-derived products may play a crucial role as source of new active compounds. In this research, a lipophilic extract of Onosma visianii roots extract containing 12% of shikonin derivatives demonstrated significant toxicity and inhibition of oviposition against Tetranychus urticae mites. Extensive chromatographic separation allowed the isolation of 11 naphthoquinone derivatives that were identified by spectral techniques and were tested against Tetranychus urticae. All the isolated compounds presented effects against the considered mite and isobutylshikonin (1) and isovalerylshikonin (2) were the most active, being valuable model compounds for the study of new anti-mite agents

A Critical Evaluation of Mechanical and Fire Performance of Flax Fiber Epoxy Resin Composites

In the present work, the mechanical behavior of flax fiber reinforced polymers (FFRPs) intended for racing applications is evaluated when subjected to different environmental conditions. A significant drop of mechanical performance in the presence of water (both 100% relative humidity and water submersion) is observed, highlighting also the fact that panels themselves already contain a fraction of water, probably absorbed onto the flax fibers prior their impregnation with the resin, that, where removed, may influence the mechanical behavior. Moreover, the flame behavior of the FFRP composite is also assessed in comparison with the widely applied carbon fiber reinforced polymers (CFRPs) to highlight the effect of the different reinforcement. Both FRPs are produced with the same flame retarded resin to highlight the contribution of the different reinforcement. The evaluation of the flame behavior of the FFRP panels shows that it completely burns during the cone-calorimetric test, involving in the fire both the matrix and the reinforcement with a stronger and faster heat release than the corresponding CFRP based on the same resin. The above observations seem thus to discourage their use in critical conditions, where the decrease of mechanical performance and the event of fire incidental condition may dramatically and negatively affect the final application

Optimization of Pyro-gasification of Carbon Fiber Reinforced Polymers (CFRPs)

This work focuses on the optimization of pyro-gasification process of carbon fiber reinforced polymers (CFRPs) with the aim of recovering carbon fibers (CFs) with properties suitable for the production of new more sustainable composites with high performances. In particular, the pyro-gasification process is carried out on cured CFRPs panels based on both epoxy (EC) and vinyl ester (VC) matrices, which are the two most used resins for CFRPs. The matrix degradation is evaluated via sample's weight loss measurement and the recovered CFs obtained after different time of treatment are analyzed to identify convenient pyro-gasification conditions to avoid damaging of the recovered CFs. The obtained results highlight the importance of the thickness of the composites to be treated for the identification of the more suitable pyro-gasification conditions

Hyperspectral imaging to measure apricot attributes during storage

The fruit industry needs rapid and non-destructive techniques to evaluate the quality of the products in the field and during the post-harvest phase. The soluble solids content (SSC), in terms of °Brix, and the flesh firmness (FF) are typical parameters used to measure fruit quality and maturity state. Hyperspectral imaging (HSI) is a powerful technique that combines image analysis and infrared spectroscopy. This study aimed to evaluate the potential of the application of the Vis/NIR push-broom hyperspectral imaging (400 to 1000 nm) to predict the firmness and the °Brix in apricots (180 samples) during storage (11 days). Partial least squares (PLS) and artificial neural networks (ANN) were used to develop predictive models. For the PLS, R2 values (test set) up to 0.85 (RMSEP=1.64 N) and 0.72 (RMSEP=0.51 °Brix) were obtained for the FF and SSC, respectively. Concerning the ANN, the best results in the test set were achieved for the FF (R2=0.85, RMSEP=1.50 N). The study showed the potential of the HSI technique as a non-destructive tool for measuring apricot quality even along the whole supply chain

Ovicidal activity of Pithecellobium dulce (Family: Fabaceae) leaf and seed extracts against fi lariasis vector mosquito Culex quinquefasciatus (Diptera: Culicidae)

Mosquito-borne diseases with an economic impact create a loss in commercial and labor outputs, particularly incountries with tropical and subtropical climates. Mosquito control is facing a threat because of the emergence ofresistance to synthetic insecticides. Insecticides of botanical origin may serve as suitable alternative biocontroltechniques in the future. In view of recently increased interest in developing plant origin insecticides as analternative to chemical insecticide, in the present study ovicidal efficacy of different solvent leaf and seed extractof Pithecellobium dulce against filariasis vector C. quinquefasciatus. The ovicidal efficacy of the crude leaf extractsof P. dulce with five different solvents, such as benzene, hexane, ethyl acetate, methanol, and chloroform, wastested against C. quinquefasciatus. Ovicidal activity was determined against C. quinquefasciatus mosquito tovarious concentrations ranging from 100 to 600 mg/L under the laboratory conditions. Among five solvent testedthe maximum efficacy was observed in the leaf and seed methanol crude extract was found to be most effectivefor ovicidal activity against vector mosquito. The extract of methanol exerted 100% mortality at 500-600 mg/Lagainst C. quinquefasciatus. From the result, it can be concluded the crude extract of P. dulce was a potentialcandidate to develop newer and safer ovicides against C. quinquefasciatus

A Thermoplastic Elastomeric Nanofibrous Membrane as CFRP Modifier to Boost Both Delamination and Damping Performance

In the present work, thermoplastic elastomeric nanofibers made up of a homogenous blend of nitrile butadiene rubber (NBR) and Ppolycaprolactone (CL), with 80% wt of rubbery component, are used to modify a carbon fiber reinforced polymer (CFRP) laminate with the aim of improving its delamination and damping behavior at the same time. Since the nanofibrous membrane is not chemically cross-linked, the fibrous morphology is lost during composite curing owing to its melting. Nonetheless, the nanomodified CFRP displays an impressive ability to improve the delamination resistance in mode I and also an enhanced damping capacity at low temperature. The use of nanofibrous membranes allows for modification of specifically selected areas, thus maximizing the toughening and damping behavior where most required, without necessarily affecting the whole bulk of the resin. Both PCL and NBR components contribute to the final performance; however, the very high amount of rubber leads to a membrane difficult to handle whose final performance in CFRP modification is not superior to membranes up to 60% wt NBR that are instead more stable and easier to deal with. Overall, the proposed results are nonetheless very promising, taking into account also that the improved delamination resistance in mode I and enhanced damping are obtained without significantly sacrificing the weight and overall dimension of the obtained composite

Rubbery nanofibers by co-electrospinning of almost immiscible NBR and PCL blends

The paper presents a simple method for producing rubbery nanofibers without additional crosslinking required. Electrospinning's fast solvent evaporation is able to induce in liquid NBR/PCL pairs thermoplastic elastomeric (TPE) structure that holds stable over time without any further processing. The slight relative solubility of the polymers pair promotes a homogeneous blend formation with low Tg regions of blended NBR/PCL, avoiding phase separation. Such nanofibers show also a PCL-like crystal phase that is surprisingly higher than plain PCL nanofibrous counterpart and seemingly promoted by NBR/PCL interaction at molecular scale. The obtained nanofibrous-TPE morphology is reproducible, stable with time up to at least two years and is detected in a wide range of blend compositions (up to 80%wt NBR). Such a morphology reflects in good mechanical properties, which are analysed with a fitting model taking into account nanofibrous structure. Its impressive fitting ability helps interpretation of tensile tests behavior, carried out via normalization of force data with respect to sample mass, highlighting the contribution of liquid rubber in improving both elastic modulus and properties at failure. Such rubbery nanofibers represent a cost-effective powerful tool for the production of advanced self-damping composite materials with improved overall mechanical properties

Oviposition inhibitory activity of the Mexican sunflower Tithonia diversifolia (Asteraceae) polar extracts against the two-spotted spider mite Tetranychus urticae (Tetranychidae)

The Mexican sunflower (Tithonia diversifolia, Asteraceae) is an invasive shrub of agricultural and non-agricultural lands in tropical countries. Besides extensive utilizations in the traditional medicine, mainly to treat malaria, the plant is believed to have a great potential in agriculture of developing countries as a green biomass to produce fertilizer, fodder and biopesticides. The plant is known to produce tagitinins, which are sesquiterpene lactones with a bitter taste endowed with toxicity against several insects such as mosquitoes, aphids, and beetles. Here, we evaluated the potential of T. diversifolia against the two-spotted spider mite Tetranychus urticae (Tetranychidae), which is one of the most economically important arthropod pests worldwide. The leaf methanolic extract and its ethyl acetate fraction were tested for acute and chronic toxicity and for oviposition inhibitory effects. The chemical composition of the extracts was analyzed by HPLC-MSn and NMR. The main constituents were flavonoid derivatives, phenylpropanoids and sesquiterpene lactones. Among the latter, tagitinin C and tagitinin A were the major compounds. In acute toxicity assays, mortality did not exceed 50% even for the highest tested dose of 150 \u3bcg cm-3. However, in chronic toxicity assays, on day 5 from application, the methanolic extract LD50 was 41.3 \u3bcg cm-3 while LD90 was 98.7 \u3bcg cm-3. Furthermore, both T. diversifolia extracts inhibited oviposition in T. urticae. The ethyl acetate extract was the most active oviposition inhibitor, with an ED50 value of 44.3 \u3bcg cm-3 and an ED90 of 121.5 \u3bcg cm-3. Overall, the good yield rate of the extract and the high crop yield highlighted good prospects of using the extract from this plant for the development of oviposition inhibitors against mite

A New Wood Surface Flame-Retardant Based on Poly-m-Aramid Electrospun Nanofibers

Poly(meta-phenylene isophtalamide) (PMIA) was processed via electrospinning to provide nanofibrous membranes with randomly and aligned fibers. Mechanical performance of such membranes was evaluated, applying a normalization procedure that takes into account the peculiar morphology of such complex substrate where voids can sum up to almost 80% of the sample volume. Random and aligned fibers membranes are applied onto wood panels to test their fire resistance in cone calorimetry when coated in polyaramidic thin nanofiber mats. Tests highlighted that random fibers provide a better fire protection, increasing Time to Ignition and decreasing the Fire Performance Index. Another important parameter affecting the performance is the adhesive system used to apply the nanofibers onto wood that is able to significantly modify the fire performance of the polyaramidic-coated wood panels. POLYM. ENG. SCI., 2019. (c) 2019 Society of Plastics Engineer

Polyamide Nanofibers Impregnated with Nitrile Rubber for Enhancing CFRP Delamination Resistance

Delamination is the main responsible for structural failure of composites having a laminar structure. In the present work, polyamide (Nylon 66) nanofibers, even impregnated with uncrosslinked nitrile butadiene rubber (NBR), are interleaved into epoxy-based carbon fiber reinforced polymer (CFRP) laminates with the aim to counteract the delamination phenomenon. The performance of nano-modified composites using both the nanofibrous mat types, that is, Nylon 66 and NBR-impregnated Nylon 66 membranes, is investigated. Mode I loading tests show a significant improvement of the interlaminar fracture toughness of rubber-modified CFRPs, especially in the G(I,)(R) (up to +151%). The improvement in the G(I,)(C) is less pronounced, but still significant (up to +80%). The achieved results are very encouraging and pave the way to the use of such Nylon-NBR hybrid mats for hindering delamination