Image recovery from undersampled data has always been challenging due to its implicit ill-posed nature but becomes fascinating with the emerging compressed sensing (CS) theory. This paper proposes a novel gradient based dictionary learning method for image recovery, which effectively integrates the popular total variation (TV) and dictionary learning technique into the same framework. Specifically, we first train dictionaries from the horizontal and vertical gradients of the image and then reconstruct the desired image using the sparse representations of both derivatives. The proposed method enables local features in the gradient images to be captured effectively, and can be viewed as an adaptive extension of the TV regularization. The results of various experiments on MR images consistently demonstrate that the proposed algorithm efficiently recovers images and presents advantages over the current leading CS reconstruction approaches.

Massive amounts of plastic waste have been released into ecosystems, generating huge amounts of microplastics (MPs) and nanoplastics (NPs) during the environmental aging process. However, particle size and number dynamics along the aging process have not been quantitatively assessed, which can greatly influence their fate and environmental risk assessment. We applied single particle inductively coupled plasma mass spectroscopy (spICP-MS) to quantitatively analyze the polystyrene (PS) MPs aging process with a wide particle size range (800 nm−5 μm) as well as particle number concentration at an environmentally relevant value (down to 7.1 × 10 6 particles/L). We investigated the UV-light accelerated aging dynamics of PS MPs and revealed the generation of large amounts of nano/microsize PS MPs fragments. PS MPs showed a rapid size downtrend along the aging process, shrinking from 5 to 1 μm. At the same time, PS MPs particle number concentration increased 3 times. Furthermore, pristine PS MPs may induce acute toxicity in feeding behavior, growth, and survival, while aged ones caused marked chronic toxicity on the reproduction inhibition of Daphnia magna, both at environmentally relevant concentrations. Overall, the research uncovered and quantified MPs particle size and concentration during the aging process, which is essential to assessing ecotoxicological risks of MPs/NPs.

Distributed compressed sensing is shown to be able to accelerate DTI and may be used to reduce DTI acquisition time practically.