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  • Payne posted an update 7 months, 2 weeks ago

    The present study investigates the layer-specific mechanical behavior of human skin. Motivated by skin’s histology, a biphasic model is proposed which differentiates between epidermis, papillary and reticular dermis, and hypodermis. Inverse analysis of ex vivo tensile and in vivo suction experiments yields mechanical parameters for each layer and predicts a stiff reticular dermis and successively softer papillary dermis, epidermis and hypodermis. Layer-specific analysis of simulations underlines the dominating role of the reticular dermis in tensile loading. Furthermore, it shows that the observed out-of-plane deflection in ex vivo tensile tests is a direct consequence of the layered structure of skin. In in vivo suction experiments, the softer upper layers strongly influence the mechanical response, whose dissipative part is determined by interstitial fluid redistribution within the tissue. Magnetic resonance imaging-based visualization of skin deformation in suction experiments confirms the deformation pattern predicted by the multilayer model, showing a consistent decrease in dermal thickness for large probe opening diameters.Nanotechnology is a new field in the pesticide industry. Nanopesticides represent an emerging technological tool that offers a range of benefits including increased efficacy, durability, and reduction in the amounts of used active ingredients. However, due to the lack of studies on the toxicity and the sublethal effects on pests and natural enemies, the extent of action and fate of these nanopesticdes is still not fully understood limitting thus their wide use. In this study, we encapsulated the pirimicarb insecticide using nanostructured lipid carriers (NLC) and investigated the toxicity and sublethal effects (LC25) of the resulting nanocapsules against the cabbage aphid, Brevicoryne brassicae (Linnaeus) (Hemiptera Aphididae) and its natural enemy the green lacewings Chrysoperla carnea (Stephens) (Neuroptera Chrysopidae). Nanoencapsulation of pirimicarb enhanced 12.6-fold its toxicity to cabbage aphids compared to its commercial formulation. Furthermore, analysis of the age-stage, two-sex life table showed that negative effects on the B. brassicae aphid population growth were observed on F0 and F1 generations when aphids of parental (F0) generation were exposed to subelethal dose (LC25) of both formulations of pirimicarb. However, negative effects from sublethal exposure to the commercial and nanoformulated pirimicarb resulted in significant reduction on the net reproductive rate, intrinsic rate of natural increase, and finite rate of increase of the green lacewings C. carnea. Our findings indicate that the approaches and assumptions used to assess the risks of conventional insecticides may not apply for nanopesticides. Further research is still needed to better understand the environmental impact of these compounds.Data concerning the toxicity of the transformation products of some pesticides considered emerging contaminants are still incipient. This study aimed to evaluate acute (filter paper contact and avoidance test) and chronic (assays carried out in Red yellow Ultisoil) effects of the transformation products of the fungicide imazalil (IMZ) by heterogeneous photocatalysis (TiO2/UV) in Eisenia andrei. Some endpoints, i.e. biomass variation, disorder in reproduction and avoidance behavior, cytotoxicity (cell density and feasibility), and coelomic fluid (eleocytes and amoebocytes, immune cell) and antioxidant system (catalase (CAT) and glutathione S-transferase (GST)) changes were assessed. The studied degradation times (6, 18, 35 and 90 min) represented 70; 35; 10 and 0% of the initial IMZ concentration (5 mg L-1). No lethality and no significant difference in biomass variations were noted in the acute contact test. Decreased GST and increased CAT activities, as well as cell typing alterations and decreased cell viability and density detected at the 90-min degradation timepoint (PDT-90) indicate direct cytotoxic IMZ transformation product effects. Cladribine ic50 In the avoidance test, no significant earthworm repulsion or attraction was observed. PDT-90 transformation products were responsible for losses in biomass and a reduction in the number of earthworm cocoons and juveniles present in soil. No cytotoxic effects were observed in the long term, although increased CAT and decreased GST activities were observed. Investigations on the relative toxicity of IMZ transformation products are relevant for future discussions regarding the environmental treatment, control and destination of this compound and its derivatives.Aquatic invertebrates can be exposed to copper from various sources, including agricultural applications. For example, concentrations up to 1000 µg L-1 are found within rice fields, where copper-containing formulations are used as fungicides and algaecides. We conducted toxicity tests to study lethal and sublethal effects of copper sulfate pentahydrate on all immature stages across two generations of Culex pipiens mosquitoes as our model organism. Mortality was dose-dependent at concentrations of 500 µg L-1 and above in the first generation, and 125 µg L-1 and above in the second generation. The median lethal concentrations (LC50) of copper sulfate pentahydrate for larval Cx. pipiens were 476 ± 30.60 µg L-1 and 348.67 ± 23.20 µg L-1 for the first and second generations, respectively. Generation one pupation decreased from 96% in controls to 48% at 500 µg L-1, while the second-generation pupation decreased from 96% in controls to 17.5% at 500 µg L-1. Mortality during the pupal stage varied from 2 to 10% at 500 µg L-1 of first and second generations, respectively. Higher levels also delayed development to adulthood in both generations. The duration of the immature period was 14.8 days in controls in both generations, but when exposed at 500 µg L-1 it increased to 18.8 days in the first generation and to 20.5 days in the second generation. The chronic, multi-generation exposures in this study showed greater toxicity than reported for shorter exposures of Cx. pipiens, and confamilial taxa like Culex hortensis and Anopheles hispaniola.

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