Selective and Controllable Cracking of Polyethylene Waste by Beta Zeolites with Different Mesoporosity and Crystallinity.

Waste plastics bring about increasingly serious environmental challenges, which can be partly addressed by their interconversion into valuable compounds. It is hypothesized that the porosity and acidity of a zeolite-based catalyst will affect the selectivity and effectiveness, enabling a controllable and selective conversion of polyethylene (PE) into gas-diesel or lubricating base oil. A series of embryonic, partial- and well-crystalline zeolites beta with adjustable porosity and acidity are prepared from mesoporous SBA-15. The catalysts and catalytic systems are studied with nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and adsorption kinetics and catalytic reactions. The adjustable porosity and acidity of zeolite-beta-based catalysts achieve a controllable selectivity toward gas-diesel or lubricating base oil for PE cracking. With a catalyst with mesopores and appropriate acid sites, a fast escape and reduced production of cracking of intermediates are observed, leading to a significant fraction (88.7%) of lubricating base oil. With more micropores, a high acid density, and strong acid strength, PE is multiply cracked into low carbon number hydrocarbons. The strong acid center of the zeolite is confirmed to facilitate significantly the activation of hydrogen (H2), and, an in situ ammonia poisoning strategy can significantly inhibit hydrogen transfer and effectively regulate the product distribution.

Competitive and sequence reactions of typical hydrocarbon molecules in diesel fraction hydrocracking - a theoretical study by DFT calculations.

The molecular structures of hydrocarbon molecules determine the competitive and sequence reactions in the diesel hydrocracking process. In this study, the hydrocracking reactions of typical hydrocarbons with various saturation degrees and molecular weights in diesel fractions synergistically catalyzed by the Ni-Mo-S nanocluster and Al-Si FAU zeolite are investigated. The results show that the two major rate-controlling steps in saturated hydrocarbon hydrocracking are dehydrogenation on the Ni-Mo-S active sites and the cracking of the C-C bonds on the FAU zeolite acid center. Moreover, the major rate-controlling step in cracking the cycloalkyl aromatic hydrocarbons is the protonation of the aromatic ring. Moreover, the aromatic hydrocarbons presented an apparent advantage in competitive adsorption on the Ni-Mo-S active sites, whereas hydrocarbons with higher molecular weights demonstrated a moderate adsorption advantage on both Ni-Mo-S active sites and FAU zeolite acid centers.

Prone Position in Treatment of Hypoxemia in Patients Who Underwent Type A Aortic Dissection Surgery.

BACKGROUND: Postoperative hypoxemia is a high-risk complication after acute type A aortic dissection (TAAD) surgery. Prone position (PP) is an effective treatment for acute respiratory failure, which may improve the gas exchange of the injured lung and the patient's survival. PP is reported to improve the respiratory condition after cardiac surgery. However, limited data exist on the effect of PP in patients who underwent acute TAAD surgery. METHODS: We retrospectively analyzed the clinical outcomes of seven patients with severe hypoxemia who underwent PP after acute TAAD surgery. The results of arterial blood gas, chest X-ray, and survival were collected. RESULTS: Seven patients (3 female, mean age 48.3±11.7 years) were recruited in this study. All patients received total arch replacement and frozen elephant trunk implantation procedure. The PaO2 at day 1 after PP was higher than before PP (126.3±49.3 vs. 77.8±15.5 mmHg). The oxygenation index rose sharply from 83.0 (80.0, 87.0) to 188.3±56.5 at day 3 after PP. There was no significant difference in heart rate between before and after PP procedure. Chest X-ray showed the diffuse shadow was significantly improved after PP. All patients responded well to PP, and all patients were discharged except for one patient, who died perioperatively due to multiple organ failure. CONCLUSIONS: PP is a safe and feasible option for severe hypoxemia patients after TAAD surgery.

Systemic Deficiency of PTEN Accelerates Breast Cancer Growth and Metastasis.

Mutation or loss of the tumor suppressor gene PTEN or its functional status in tumor stromal cells may affect tumor occurrence, development, invasion, and metastasis, in which, however, the role of overall low PTEN expression, mutation, or deletion in the tumor-bearing host has rarely been reported. Breast cancer is a common highly invasive metastatic tumor. We therefore treated mouse breast cancer 4T1 cells with the specific PTEN inhibitor VO-OHpic to study the effects of PTEN suppression or deletion on malignant behavior in vivo and in vitro. VO-OHpic effectively inhibited PTEN gene/protein expression in 4T1 cells, accelerated cell proliferation, and enhanced cell migration and invasion. We also transplanted 4T1 cells with VO-OHpic-inhibited PTEN into mice to create orthotopic and metastatic breast cancer models. The proliferation of 4T1 cells in mouse mammary gland was increased and distant metastasis was enhanced, with metastatic foci in the lung, liver, and intestinal tract. In addition, injection of mice with VO-OHpic to inhibit PTEN in the overall microenvironment accelerated the proliferation of transplanted 4T1 cells and enhanced distant metastasis and the formation of metastatic tumors. Metastatic foci formed in the lung, liver, intestine, thymus, and brain, and PTEN levels in the organ/tissues were negatively associated with the formation of metastatic foci. Similarly, inoculation of PTEN-deficient 4T1 cells into systemic PTEN-inhibited mice further enhanced the orthotopic growth and distant metastasis of 4T1 breast cancer. VO-OHpic inhibition of PTEN in 4T1 cells was also associated with significantly increased phosphorylation of Akt and phosphoinositide 3-kinase (PI3K), suggesting that inhibition of PTEN could activate the PI3K-Akt pathway, as a key signaling pathway regulating cell proliferation and death. These results confirmed that functional loss or deletion of the tumor suppressor gene PTEN significantly enhanced the proliferation, invasion, and metastasis of 4T1 cells. Systemic decrease or deletion of PTEN in the organism or organ/tissue microenvironment was conducive to the proliferation of breast cancer cells in situ and distant metastasis. These results suggest that, as well the PTEN in cancer cells the systemic microenvironment PTEN intensely mediates the proliferation, invasion and metastasis of mouse breast cancer cells via regulating the PI3K-Akt signaling pathway.

Association analysis of ERCC5 gene polymorphisms with risk of breast cancer in Han women of northwest China.

BACKGROUND: ERCC5 plays an important role in DNA damage repair. Mutations in it will lead to DNA repair defects and genomic instability. Its functional single nucleotide polymorphisms (SNPs) may alter DNA repair capacity and affect cancer susceptibility. METHODS: This study aims to evaluate the association between SNPs in ERCC5 and breast cancer susceptibility in Han women subjects genetically from northwest China. A total of 101 breast cancer patients and 101 healthy controls provided blood samples for analysis of ERCC5 rs17655 and rs751402 genotypes. RESULTS: After adjusting covariates, rs751402 homozygote AA and heterozygote AG were found to confer statistically significant protections (OR 0.052, 95% CI 0.006-0.411, P = 0.005; OR 0.145, 95% CI 0.067-0.315, P < 0.001, respectively) against breast cancer. Moreover, both of the dominant and recessive models of rs751402 also conferred a decreased risk of breast cancer (AA + AG vs. GG, OR 0.125, 95% CI 0.060-0.261, P < 0.001; AA vs. GG + AG, OR 0.082, 95% CI 0.010-0.648, P = 0.018, respectively). CONCLUSIONS: The results indicate that the rs751402 in ERCC5 may affect the risk of breast cancer and show that it is associated with breast cancer characteristics in the Han population of northwest China. However, we found no significant differences between breast cancer patients and control subjects regarding ERCC5 rs17655 polymorphism in the studied population.