Three dimensional printing technologies represent a revolution in the manufacturing sector because of their unique capabilities for increasing shape complexity while reducing waste material, capital cost and design for manufacturing. However, the application of 3D printing technologies for the fabrication of functional components or devices is still an almost unexplored field due to their elevated complexity from the materials and functional points of view. This paper focuses on reviewing previous studies devoted to developing 3D printing technologies for the fabrication of functional parts and devices for energy and environmental applications. The use of 3D printing technologies in these sectors is of special interest since the related devices usually involve expensive advanced materials such as ceramics or composites, which present strong limitations in shape and functionality when processed with classical manufacturing methods. Recent advances regarding the implementation of 3D printing for energy and environmental applications will bring competitive advantages in terms of performance, product flexibility and cost, which will drive a revolution in this sector.
Broader contextIntensive research on additive manufacturing has been carried out during the last three decades to allow the fabrication of three dimensional objects by assembling materials without the use of tools or molds. Three dimensional printing technologies represent a potentially low-cost, new paradigm for the manufacture of energy conversion technologies offering unique capabilities in terms of shape/geometry complexity and enhancement of specific performance per unit of mass and volume of the 3D printed units. However, the fabrication of highly complex devices for the energy sector by using 3D printing is an almost unexplored field. In this work we review the state of the art of 3D printing technology to fabricate components or devices for energy and environmental applications, focusing on aspects related to the control of the microstructure, functionality and performance of the 3D printed structures.
Polycyclic aromatic hydrocarbons (PAHs) are a family of toxicants that are ubiquitous in the environment. These contaminants generate considerable interest, because some of them are highly carcinogenic in laboratory animals and have been implicated in breast, lung, and colon cancers in humans. Dietary intake of PAHs constitutes a major source of exposure in humans. Factors affecting the accumulation of PAHs in the diet, their absorption following ingestion, and strategies to assess risk from exposure to these hydrocarbons following ingestion have received very little attention. This review, therefore, focuses on concentrations of PAHs in widely consumed dietary ingredients along with gastrointestinal absorption rates in humans. Metabolism and bioavailability of PAHs in animal models and the processes, which influence the disposition of these chemicals, are discussed. Finally, based on intake, disposition, and tumorigenesis data, the exposure risk to PAHs from diet is presented. This information is expected to provide a framework for refinements in risk assessment of PAHs.
Dioxins include polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and part of polychlorinated biphenyls (PCBs). Only the compounds that are chlorinated at the 2,3,7, and 8 positions have characteristic dioxin toxicity. PCDDs, PCDFs and PCBs accumulate in the food chain due to their high lipophilicity, high stability, and low vapor pressure. They are not metabolized easily; however their hydroxylated metabolites are detected in feces. They cause a wide range of endocrine disrupting effects in experimental animals, wildlife, and humans. Endocrine related effects of PCDDs, PCDFs and PCBs on thyroid hormones, neurodevelopment and reproductive development were referenced. In addition, some studies of contamination of foods, bioaccumulation, dietary exposure assessment, as well as challenges of scientific research in these compounds were reviewed.
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