Zero-Watermarking for Vector Maps Combining Spatial and Frequency Domain Based on Constrained Delaunay Triangulation Network and Discrete Fourier Transform.

With its lossless properties, zero-watermarking has attracted a lot of attention in the field of copyright protection for vector maps. However, the common zero-watermarking algorithm puts too much emphasis on mining for global features, making it vulnerable to cropping attacks, and the robustness is not comprehensive enough. This study provides a vector map zero-watermarking scheme that utilizes spatial statistical information and frequency domain transformation methods in an effort to solve the aforementioned issue. In order to make the scheme more resistant to cropping and compression, it is constructed on the basis of feature point extraction and point constraint blocking of the original vector map. Within each sub-block, feature points are used to build constraint Delaunay triangulation networks (CDTN), and the angular values within the triangle networks are then extracted as spatial statistics. The angle value sequence is further transformed by discrete Fourier transform (DFT), and the binarized phase sequence is used as the final feature information to build a zero watermark by executing an exclusive disjunction operation with the encrypted copyright watermark image, both of which contribute to the scheme's robustness and security. The results of the attack experiments show that the proposed vector map zero-watermarking can restore identifiable copyright images under common geometric attacks, cropping attacks, and coordinate system transformations, demonstrating a high level of robustness. The theoretical basis for the robustness of this watermarking scheme is the stability of CDTN and the geometric invariance of DFT coefficients, and both theory and experiment validate the method's validity.

An efficient method for extracting microplastics from feces of different species.

Concerns have been raised regarding the ingestion of microplastics (MPs) by numerous organisms including humans. However, no efficient and standardized methods are available for extracting MPs from feces. In this study, we introduce a novel approach with high digestion efficiency that involves using Fenton's reagent and nitric acid to remove feces solids. Firstly, Fenton's reagent was used to degrade small solids and decompose large solids into small pieces. Secondly, nitric acid was used to digest the remaining solids and filters. Furthermore, absolute ethyl alcohol was used to remove the mineral residues wrapped on the plastic surfaces and disperse MPs. By using this method, 97.78 % MPs can be recovered from human and chicken feces, and no significant changes were observed in the physical and Raman spectral properties of different polymer types of MPs. This method has also been verified by extracting MPs from field feces. Overall, the proposed method can efficiently digest feces solids and extract MPs with higher recovery rate, less intermediate steps and less damage, which can serve as an economical and feasible method for the detection of MPs in the feces of different species.

Accumulation of different shapes of microplastics initiates intestinal injury and gut microbiota dysbiosis in the gut of zebrafish.

Different shapes of microplastics are widely detected in the environment and organisms and most of them remain in the gut. However, the influences of shapes on the bioaccumulation and toxicity of microplastics in the gut are largely unknown. Three shapes (bead, fragment, and fiber) of microplastics of comparable size in one dimension were prepared to exposure to zebrafish. The accumulation and toxicities of microplastics in the gut were detected. Shape-dependent accumulation in the gut was observed with the order of fibers (8.0 µg/mg) > fragments (1.7 µg/mg) > beads (0.5 µg/mg). The accumulation of microplastics caused multiple toxic effects in fish intestine, including mucosal damage, and increased permeability, inflammation and metabolism disruption. Based on these toxic effects, microplastic fibers resulted in more severe intestinal toxicity than microplastic fragments and beads did. Furthermore, microplastics also induced gut microbiota dysbiosis and specific bacteria alterations, which will provide novel insights into the potential mechanism of microplastics causing intestinal toxicities in fish. Our results also suggested that shape-depended effects should not be ignored in the health risk assessment of microplastics.