Formation and toxicity alteration of halonitromethanes from Chlorella vulgaris during UV/chloramination process involving bromide ion.

Frequent algal blooms cause algal cells and their algal organic matter (AOM) to become critical precursors of disinfection by-products (DBPs) during water treatment. The presence of bromide ion (Br-) in water has been demonstrated to affect the formation laws and species distribution of DBPs. However, few researchers have addressed the formation and toxicity alteration of halonitromethanes (HNMs) from algae during disinfection in the presence of Br-. Therefore, in this work, Chlorella vulgaris was selected as a representative algal precursor to investigate the formation and toxicity alteration of HNMs during UV/chloramination involving Br-. The results showed that the formation concentration of HNMs increased and then decreased during UV/chloramination. The intracellular organic matter of Chlorella vulgaris was more susceptible to form HNMs than the extracellular organic matter. When the Br-: Cl2 mass ratio was raised from 0.004 to 0.08, the peak of HNMs total concentration increased 33.99%, and the cytotoxicity index and genotoxicity index of HNMs increased 67.94% and 22.80%. Besides, the formation concentration and toxicity of HNMs increased with increasing Chlorella vulgaris concentration but decreased with increasing solution pH. Possible formation pathways of HNMs from Chlorella vulgaris during UV/chloramination involving Br- were proposed based on the alteration of nitrogen species and fluorescence spectrum analysis. Furthermore, the formation laws of HNMs from Chlorella vulgaris in real water samples were similar to those in deionized water samples. This study contributes to a better comprehension of HNMs formation from Chlorella vulgaris and provides valuable information for water managers to reduce hazards associated with the formation of HNMs.

Numerical Evaluation on Residual Thermal Stress-Induced Delamination at PDMS-Metal Interface of Neural Prostheses.

The most common failure mode of implantable neural implants has been delamination of layers in compound structures and encapsulations in a wet body environment. Current knowledge of failure mechanisms of adhesion and its standardized test procedures are lacking and must be established. This study demonstrated a combined experimental and numerical method to investigate the residual stresses from one of the most common encapsulation materials, silicone rubber (polydimethylsiloxane-PDMS) during the coating process at elevated temperatures. Measured shrinkage of test specimen correlates well to a modified shrinkage model using thermal-mechanical finite element method (FEM) simulation. All simulated interfacial stresses show stress concentration at the PDMS coating front depending on curing temperature and coating thickness, while Griffith's condition estimated the delamination of the coating front. This study emphasizes the understanding of the interfacial delamination giving the possibility to predict failure mode of neural interface.