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Graphical Abstract:

Proton exchange membrane fuel cells (PEMFCs) are one of the most promising power sources in the fields of vehicle and ship power. Compression caused by assembly pressure, freeze-thaw cycles, and mechanical vibration can cause changes in the microstructure of the gas diffusion layer (GDL), thereby affecting the mass transfer and electrochemical reaction processes inside the PEMFC. In this paper, a three-dimensional single-phase multi-component lattice Boltzmann (LB) model is established to investigate the effects of binder volume fraction and compression on the cathode electrochemical performance. The stochastic reconstruction method is employed to generate 20 GDLs with different binder volume fractions and compression ratios. Afterward, the reactive gas flow within the 20 GDLs is simulated, and the distribution of oxygen mole fraction, water vapor mole fraction, and the current density are analyzed. The simulation results demonstrate that the mean current density decreases with the increase of the compression ratio, and the optimal binder volume fraction of 20% resulted in the highest current density. This paper enriches the research on the cathode electrochemical performance of PEMFCs at the pore scale and provides a guideline for optimizing the GDL design.

Abstract: Objective: To investigate expression of proliferating cell nuclear antigen (PCNA) in ovarian epithelial cancer and its relation to lymph node metastasis, outcome of second-look laparotomy (SLL) and prognosis. Methods: Monoclonal antibody PC10 was used to stain PCNA in archival paraffin-embedded tissues. Results: PC10 immunostaining was performed successfully in all 74 primary and 31 intraperitoneal metastatic tumors. The expression levels of PCNA were significantly increased in 31 metastatic tumors compared with their primary tumor from the same patients (7.94 vs 6.89,P=0.042). The expression levels was more elevated in bilateral than in unilateral ovarian cancer, but it was not associated with lymph node metastasis, clinical stage, histological grade and subtype. In 28 patients with stage III ovarian cancer undergone SLL, the mean immunoreactive score (IRS) of PCNA of the primary tumor was significantly higher in patients with negative SLL than in those with positive SLL (7.59 vs 6.10,P=0.03). Since chemotherapy was performed following surgical debulking, negative SLL more frequently seen in patients with high PCNA expression might suggest better chemotherapeutic sensitivity due to higher proliferation fraction of tumor cell. Univariate analysis of survival indicated that the overall survival was inversely associated with the level of PCNA expression, while multivariate analysis with Cox’s model showed that independent prognostic factors were the residual tumor after primary debulking (P<0.001) and clinical stage (P<0.05), followed by PCNA expression (P=0.09). Conclusion: The expression of PCNA may be useful in predicting the patients’ prognosis, but is not correlated with lymph node metastasis.

Abstract: Objective: To identify the loss of heterozygosity (LOH) on chromosome 17p13.3 in ovarian cancer and cervical cancer. Methods: The frequency of LOH on chromosome 17p13.3 in DNA samples from 24 ovarian cancers, 9 cervical cancers, and 13 non-malignant gynecological diseases were determined respectively, using Southern blot method with probe PYNZ.22. Results: LOH on 17p13.3 was found in 12 of 24 (50.0%) ovarian cancers (including a borderline mucinous cystadenoma), 4 of 9 (44.4%) cervical carcinomas, and 1 of 13 (7.7%) nonmalignant gynecological diseases, which was cervical intraepithelial neoplasm III (CIN III) (P<0.01). Conclusion: These results show that LOH on 17p13.3 is associated with ovarian cancer and cervical cancer, suggesting that detection of LOH on 17p13.3 may be helpful to understand the molecular pathogenesis of ovarian cancer and cervical cancer.

The mesoscopic three-dimensional (3D) lattice Boltzmann (LB) model is employed to investigate the transport parameters for the gas diffusion layer (GDL) of a proton-exchange membrane fuel cell, and the corresponding correlations are proposed. The effects of the binder and the compression caused by the assembly pressure on the permeability, diffusivity, and tortuosity are discussed. The GDL fiber skeleton samples are first reconstructed using the stochastic reconstruction algorithm, and samples with various binder volume fractions and various compression ratios are generated. The 3D LB model is subsequently implemented to simulate the single-phase gas flow characteristics in the GDL, and the transport parameters are calculated after the fluid reached the steady state. The simulation results indicate that the increase in the binder volume fraction and compression ratio results in a more complex GDL structure, leading to a decline in permeability and diffusivity and an increase in tortuosity. The fitted multi-factor transport parameter prediction correlations that consider fiber skeleton porosity, binder volume fraction, and compression ratio have more accurate prediction characteristics than the single-factor transport parameter prediction correlations that only consider the GDL porosity.

The effect of binder and compression on the transport parameters of the multilayer gas diffusion layer (GDL) is numerically studied by the lattice Boltzmann method. A stochastic algorithm is implemented to generate three multilayer GDLs with a porosity gradient and a uniform GDL, and then, the GDLs are compressed after the binder is added to obtain structures with various binder volume fractions and various compression ratios. The pore size distribution, through-plane (TP) permeability, in-plane (IP) permeability, tortuosity, and electric conductivity of the four structures of GDLs are analyzed. The pore size distributions of GDLs move toward smaller pores due to compression, and the GDL with a larger porosity gradient has a larger maximum pore size. The TP permeability decreases with the increase of compression ratio and binder volume fraction, and the TP permeability of the four GDLs decreases similarly due to compression, but the TP permeability of the multilayer GDL with a larger porosity gradient drops more due to the binder. IP permeability is slightly affected by the compression. Similar to TP permeability, the IP permeability of the multilayer GDL with a large porosity gradient decreases more due to the binder. Multilayer GDL with a small porosity gradient has a smaller tortuosity, more superior pore connectivity, and thus more outstanding gas permeability. The electric conductivity increases with the increase in compression ratio and binder volume fraction.