Chlorine and Bromine Isotope Fractionation of Halogenated Organic Pollutants on Gas Chromatography Columns

Compound-specific chlorine/bromine isotope analysis (CSIA-Cl/Br) has become a useful approach for degradation pathway investigation and source appointment of halogenated organic pollutants (HOPs). CSIA-Cl/Br is usually conducted by gas chromatography-mass spectrometry (GC-MS), which could be negatively impacted by chlorine and bromine isotope fractionation of HOPs on GC columns. In this study, 31 organochlorines and 4 organobromines were systematically investigated in terms of Cl/Br isotope fractionation on GC columns using GC-double focus magnetic-sector high resolution MS (GC-DFS-HRMS). On-column chlorine/bromine isotope fractionation behaviors of the HOPs were explored, presenting various isotope fractionation modes and extents. Twenty-nine HOPs exhibited inverse isotope fractionation, and only polychlorinated biphenyl-138 (PCB-138) and PCB-153 presented normal isotope fractionation. And no observable isotope fractionation was found for the rest four HOPs, i.e., PCB-101, 1,2,3,7,8-pentachlorodibenzofuran, PCB-180 and 2,3,7,8-tetrachlorodibenzofuran. The isotope fractionation extents of different HOPs varied from below the observable threshold (0.50%) to 7.31% (PCB-18). The mechanisms of the on-column chlorine/bromine isotope fractionation were tentatively interpreted with the Craig-Gordon model and a modified two-film model. Inverse isotope effects and normal isotope effects might contribute to the total isotope effects together and thus determine the isotope fractionation directions and extents. Proposals derived from the main results of this study for CSIA-Cl/Br research were provided for improving the precision and accuracy of CSIA-Cl/Br results. The findings of this study will shed light on the development of CSIA-Cl/Br methods using GC-MS techniques, and help to implement the research using CSIA-Cl/Br to investigate the environmental behaviors and pollution sources of HOPs.Comment: 30 pages, 5 figure

Two positive solutions for a nonlinear four-point boundary value problem with a p-Laplacian operator

In this paper, we study the existence of positive solutions for a nonlinear four-point boundary value problem with a $p$-Laplacian operator. By using a three functionals fixed point theorem in a cone, the existence of double positive solutions for the nonlinear four-point boundary value problem with a $p$-Laplacian operator is obtained. This is different than previous results

Influence of Body Mass Index on Comfort and Parametric Optimization Design of Seat

The influence of body mass index (BMI) on seat comfort was studied. 50 subjects were tested for body pressure distribution experiment about seat factors and BMI, and 118 subjects were tested for comfort survey experiment about the factors combination of seat height, backrest angle, and different body type on the perception of comfort. The experimental results revealed that there was positive correlation between the perception of comfort of foot and shin, foot and front of thigh, foot and back, foot and shoulder, foot and waist, with Pearson\u27s correlation coefficients of 0,608; 0,584: 0,672 and 0,620 (p < 0,05) and 0,853 (p < 0,01) respectively. Besides, there was negative correlation between body type and maximum pressure, body type and average pressure gradient, body type and maximum pressure gradient, with Pearson\u27s correlation coefficients of −0,673; −0,589 and −0,635 (p < 0,05) respectively. This study found that there was negative correlation between body type and shin, contact area and front of thigh, average pressure and front of thigh, average pressure and shoulder, with Pearson\u27s correlation coefficients of −0,769 (p < 0,01); −0,636; −0,682 and -0,605 (p < 0,05) respectively. In addition, this study also found positive correlations between maximum pressure and shin, average pressure gradient and front of thigh, maximum pressure gradient and front of thigh, average pressure gradient and shin, maximum pressure gradient and shin, with Pearson\u27s correlation coefficients of 0,681; 0,638; 0,694 (p < 0,05); 0,765 and 0,785 (p < 0,01) respectively. Moreover, when the seat height was set as knee height, and backrest angle was set as 120°, the subjective evaluation scores of three body types\u27 subjects were the highest. This study provided additional evidence that seat parameters may be a design approach for improving different body type user\u27s experience

Analysis on Causes and Countermeasures of Bullwhip Effect

Bullwhip effect is an inevitable phenomenon in supply chain management, because of its objective existence. This phenomenon is very common and harmful to make the operating costs of enterprises double and become one of the main concerns of many enterprises. In this paper, the causes of the bullwhip effect are explored through the methods of literature research and investigated consultation to weaken the bullwhip effect. This paper analyzes the key countermeasures with Wal-Mart successful logistics management case. And according to the reason of bullwhip effect, a mathematical programming model of maximizing the efficiency of supply chain is established, which provides a way to solve the negative effect of bullwhip effect and has certain reference value

Microwave Breast Imaging Techniques and Measurement Systems

Electromagnetic waves at microwave frequencies allow penetration into many optically non-transparent mediums such as biological tissues. Over the past 30 years, researchers have extensively investigated microwave imaging (MI) approaches including imaging algorithms, measurement systems and applications in biomedical fields, such as breast tumor detection, brain stroke detection, heart imaging and bone imaging. Successful clinical trials of MI for breast imaging brought worldwide excitation, and this achievement further confirmed that the MI has potential to become a low-risk and cost-effective alternative to existing medical imaging tools such as X-ray mammography for early breast cancer detection. This chapter offers comprehensive descriptions of the most important MI approaches for early breast cancer detection, including reconstruction procedures and measurement systems as well as apparatus

Global Adversarial Attacks for Assessing Deep Learning Robustness

It has been shown that deep neural networks (DNNs) may be vulnerable to adversarial attacks, raising the concern on their robustness particularly for safety-critical applications. Recognizing the local nature and limitations of existing adversarial attacks, we present a new type of global adversarial attacks for assessing global DNN robustness. More specifically, we propose a novel concept of global adversarial example pairs in which each pair of two examples are close to each other but have different class labels predicted by the DNN. We further propose two families of global attack methods and show that our methods are able to generate diverse and intriguing adversarial example pairs at locations far from the training or testing data. Moreover, we demonstrate that DNNs hardened using the strong projected gradient descent (PGD) based (local) adversarial training are vulnerable to the proposed global adversarial example pairs, suggesting that global robustness must be considered while training robust deep learning networks.Comment: Submitted to NeurIPS 201