Coupling of material point and continuum discontinuum element methods for simulating blast-induced fractures in rock

A rock blasting simulation method is proposed that couples the material point method (MPM) and continuum discontinuum element method (CDEM). Blast-induced rock fractures are captured by the CDEM using normal and shear springs, and the explosive detonation is simulated by the MPM with a Jones-Wilkins-Lee equation of state. A particle-surface/edge contact method is introduced into the MPM-CDEM to calculate the interaction between the detonation products and rock medium. Three numerical examples are presented to verify the effectiveness of the proposed method. The fracture degree is represented as the ratio of the number of fractured springs to the total number of springs, and is used to analyze the evolution of shear and tension cracks under blasting. The simulation results show that the proposed numerical method well simulates blast-induced rock fractures and considers both progressive rock fracturing and the real explosive detonation. In particular, the expansion of the detonation gas, crushed zone around the blasthole, radial cracks, and effects of pre-existing stress on the blast-induced fractures are all successfully simulated

Synthesis and Characterization of a Pentiptycene-Derived Dual Oligoparaphenylene Nanohoop

Structural designs combining oligoparaphenylene-derived nanohoops with other functional organic building blocks should lead to novel molecular architectures with intriguing properties. Herein, we describe the synthesis of a pentiptycene-derived chiral dual nanohoop molecule with key steps including ring expansion through dianthracene cycloreversion and transannular [4+2] cycloaddition across a 64-membered macrocycle. The crystal structure of the nanohoop molecule displays an ordered packing pattern with long-range channels in the solid state. Furthermore, nonracemizable enantiomers of the nanohoop were obtained through resolution and exhibited promising chiroptical properties

Synthesis of Oligoparaphenylene-Derived Nanohoops Employing an Anthracene Photodimerization-Cycloreversion Strategy

The century-old yet synthetically underexplored anthracene photodimerization-cycloreversion reactions have been employed as the key steps to access highly strained aromatic hydrocarbons. Herein we report the chemical syntheses of oligoparaphenylene-derived nanohoops in five steps or less featuring a rigid dianthracene synthon. The newly synthesized nanohoops display intriguing experimental and computational properties

Individual and Combined Toxicities of Benzo[a]pyrene and 2,2',4,4'-Tetrabromodiphenyl Ether on Early Life Stages of the Pacific Oyster, Crassostrea gigas

Persistent organic pollutants (POPs) are ubiquitous and coexisted in the aquatic environment. Individual and combined toxic effects of benzo[a]pyrene (BaP) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on embryogenesis, and larval survival of the Pacific oyster were investigated. The EC50 values of BaP, BDE-47 and their mixture on embryogenesis were 18.4, 203.3 and 72.0 A mu g/L respectively, while the LC50 values for 96 h larval mortality were 26.8, 244.5 and 108.9 A mu g/L respectively. The Marking-Dawson additive toxicity indices were -0.02 and -0.19, indicating an additive effect with a trend to antagonism. In addition, DNA strand breaks were also observed in oyster embryos after exposure. Our study suggests that BaP and BDE-47 exposure can cause developmental abnormalities, DNA damage and larval mortality. Furthermore, the toxicity of the mixture is slightly lower than individual pollutant. These data will be helpful to predict the toxicity of organic pollutants, and provide criteria for marine water quality standards

Benzo(a)pyrene-induced metabolic responses in Manila clam Ruditapes philippinarum by proton nuclear magnetic resonance ((1)H NMR) based metabolomics

Benzo(a)pyrene is an important polycyclic aromatic hydrocarbon (PAH) which causes carcinogenic, teratogenic and mutagenic effects in various species and the level of contamination of this toxic agent in the marine environment is of great concern. In this study, metabolic responses induced by two doses (0.02 and 0.2 mu M) of BaP were characterized in the gill tissues of Manila clam Ruditapes philippinarum after exposure for 24, 48 and 96h. The high dose (0.2 mu M) of BaP induced the disturbances in energy metabolism and osmotic regulation based on the metabolic biomarkers such as succinate, alanine, glucose, glycogen, branched chain amino acids, betaine, taurine, homarine, and dimethylamine in clam gills after 24 h of exposure. In addition, hormesis induced by BaP was found in clams exposed to both doses of BaP. Overall, our results demonstrated the applicability of metabolomics for the elucidation of toxicological effects of marine environmental contaminants in a selected bioindicator species such as the Manila clam. (C) 2011 Elsevier B.V. All rights reserved

An integrative biomarker approach to assess the environmental stress in the north coast of Shandong Peninsula using native oysters, Crassostrea gigas (vol 112, pg 318, 2016)

An integrative biomarker approach was employed to evaluate the environmental quality of the north coast of Shandong Peninsula along the southern Bohai Sea of China, where pollution is an imminent threat due to rapid urbanization and industrialization. A battery of biomarkers and the metal bioaccumulation in tissues of native oyster Crassostrea gigas were measured under field conditions. Integrative biomarker index (IBR) and metal body burden were calculated to differentiate the pollution status of seven sampling sites. According to our results, Xinzhuang (XZ) site was the most severely contaminated, with the highest IBR value of 3.58, while the lowest IBR value (0.04) was obtained at Penglai (PL). Such an integrated biomarker approach was proved as a useful method for environmental quality assessment in the study area. (C) 2016 Published by Elsevier Ltd