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The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions. An important challenge to be solved urgently is the reduction of imidization temperature. In this work, twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200 °C, in the absence or presence of imidazole used as the catalyst. The molecular rigidity and free volume were theoretically calculated, and relationship between structure and properties were systematically studied. The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecular chains. The rigid structure of polyimide is not conducive to the low-temperature imidization, but this adverse effect can be eliminated by adding catalyst, resulting the notably increased imidization degree. The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system, resulting in relatively higher heat resistance and thermal stability. While the mechanical performance could be determined by complicating factors, greatly different from polyimide films prepared by high temperature method. To investigate aggregation structures of films, the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated. This work can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research, and will provide guidance for the low-temperature preparation of high-performance polyimides. [ABSTRACT FROM AUTHOR]

Based on the action of the mapping class group on the space of measured foliations, we construct a new boundary of the mapping class group and study the structure of this boundary. As an application, for any point in Teichmüller space, we consider the orbit of this point under the action of the mapping class group and describe the closure of this orbit in the Thurston compactification and the Gardiner–Masur compactification of Teichmüller space. We also construct some new points in the Gardiner–Masur boundary of Teichmüller space. [ABSTRACT FROM AUTHOR]

A new cocrystal of baicalein, possessing three A-ring-hydroxyl groups and without B-ring-hydroxyl groups and 4,4′-bipyridine (BE·2BPY·H2O) has been prepared and characterized. The structural analyses and Hirshfeld surfaces show that baicalein is hydrogen-bonded to co-crystallized solvent water molecules featuring for example motifs that can be described with graph set R44(8) similar to those reported for the cocrystal of myricetin with 4,4′-bipyridine. A zipper-type architecture is observed in cocrystal BE·2BPY·H2O linking a baicalein, two 4,4′-bipyridine and a solvent water molecules via classical O–H⋯N and O–H⋯O and non-classical C–H⋯O hydrogen bonds into 2D sheets. Additionally, the cocrystal shows better solubility in 0.1 M HCl in comparison to pure baicalein. Cocrystal of baicalein with zipper-type architecture shows improved solubility compared to baicalein. [ABSTRACT FROM AUTHOR]

The 14-3-3 proteins are highly conserved molecules that are involved in many vital biologic processes and are associated with the progression of cancer. The role of 14-3-3ζ, a dimeric isoform of 14-3-3, in intrahepatic cholangiocarcinoma (ICC) was investigated in this study. The expression of 14-3-3ζ in tumour samples from patients with ICC was examined by Western blot and immunohistochemistry, and the correlation between its expression and various clinicopathological features was determined. Then, the capacity for invasion, migration and proliferation as well as the expression of epithelial-mesenchymal transition (EMT)-related markers in ICC cells were assessed after 14-3-3ζ depletion. Finally, the prognostic significance of 14-3-3ζ in patients with ICC was further evaluated by Kaplan-Meier and Cox regression analyses. The expression of 14-3-3ζ was significantly higher in ICC tissues compared to peritumoural tissues. High expression of 14-3-3ζ positively correlated with lymphatic metastasis and tumour-node-metastasis (TNM) stage. The inhibition of 14-3-3ζ expression was able to impair the invasion, migration and proliferation of ICC cells in vitro. The expression of 14-3-3ζ was significantly correlated with the expression of the EMT-related markers snail and E-cadherin in ICC samples. Moreover, the down-regulation of 14-3-3ζ also decreased the phosphorylation of extracellular signal-regulated kinase (ERK) in ICC cells. Clinically, patients with ICC with high 14-3-3ζ expression demonstrated a poor prognosis in terms of a short overall survival and a high recurrence rate of the disease. A multivariate analysis revealed that 14-3-3ζ overexpression was an independent prognostic indicator for patients with ICC. 14-3-3ζ may enhance the invasive and proliferative capacity of tumour cells and thus prompt the progression of ICC via the activation of ERK signalling and the induction of EMT. The overexpression of 14-3-3ζ may be used as a prognostic biomarker and therapeutic target in patients with ICC. [ABSTRACT FROM AUTHOR]

Aim:To investigate the role of extracellular signal-regulated kinases (ERKs) in sevoflurane post-conditioning induced cardioprotection in vitro.Methods:Isolated rat hearts were subjected to 30 min ischemia followed by 120 min reperfusion (I/R). Sevoflurane post-conditioning was carried out by administration of O2-enriched gas mixture with 3% sevoflurane (SEVO) for 15 min from the onset of reperfusion. Cardiac functions, myocardial infarct size, myocardial ATP and NAD+ contents, mitochondrial ultrastructure, and anti-apototic and anti-oncosis protein levels were measured.Results:Sevoflurane post-conditioning significantly improved the heart function, decreased infarct size and mitochondria damage, and increased myocardial ATP and NAD+ content in the I/R hearts. Furthermore, sevoflurane post-conditioning significantly increased the levels of p-ERK and p-p70S6K, decreased the levels of porimin, caspase-8, cleaved caspase-3, and cytosolic cytochrome c in the I/R hearts. Co-administration of the ERK1/2 inhibitor PD98059 (20 μmol/L) abolished the sevoflurane-induced protective effects against myocardial I/R.Conclusion:Sevoflurane post-conditioning protects isolated rat hearts against myocardial I/R injury and inhibits cell oncosis and apoptosis via activation of the ERK1/2 pathway. [ABSTRACT FROM AUTHOR]

Hollow core slabs are becoming of increasing interest as the construction industry attempts to minimise the impact of its activities on the environment. By forming voids in the interior of a concrete slab, the amount of concrete used can be reduced without significantly altering the capacity of the structure. In this study, we examined the inner force transfer mechanism of a column-supported cast-in-situ hollow core slab using finite element analysis. Both a hollow core slab and the corresponding solid slab were analysed using ANSYS and the results were compared. The orientation of the tube fillers causes the stiffness of the hollow slab to be orthotropic, potentially changing the distribution of load carried in the two orthogonal directions. Both the cross-section's moments in the column strip and near the columns in the hollow core slab become larger than that in the solid floor. As well, the cross-section's stiffness along the tube arrangement direction is larger than that of the radial cross-section, which causes the direction along the hole of the hollow core slab to carry more moment than the radial direction. The conversion factors of the two directions are proposed from the comparison for four typical areas of the hollow core slab, as are the moment distribution coefficients. [ABSTRACT FROM AUTHOR]

Isolated smooth muscle cells of the buccal mass of Aplysia contracted in response to depolarization elicited by a patch electrode in whole-cell configuration. With cesium-containing pipet solution and tetraethylammonium and 4-aminopyridine in the external solution depolarization elicited inward current. The voltage-dependent inward current was blocked completely by lanthanum (10 mmol·1), inhibited 80-90% by nifedipine (1 μmol·l), and was dependent upon extracellular calcium. These results showed that the voltage-dependent inward current was due to activation of voltage-dependent calcium channels (VDCaCH). Minimal depolarization to begin activating VDCaCH was-60 to-30 mV. Inward current peaked within 8 ms and then decreased rapidly to a lower level of relatively non-inactivating current. The initial peak current could be mostly inactivated by a depolarization to-20 mV for 500 ms. Nifedipine reduced both the peak current and the relatively non-inactivating current. Nifedipine inhibited high potassium-elicited contractions of both intact and dissociated muscle. These results suggested that VDCaCH mediates calcium influx which triggers contraction in molluscan smooth muscle fibers. [ABSTRACT FROM AUTHOR]

Forty-five patients suffering from angina pectoris of coronary heart disease (CHD) were successfully treated with Tianbaoning (TBN). The effect of the treatment was compared with that of nifedipine. The clinical practice showed that the group treated with TBN showed better results. After medication, the patients were markedly relieved from angina pectoris of CHD. Meanwhile the improvement of electrocardiogram (ECG) and impedance cardiogram were also observed. The effective rate of ECG improvement was 83.7%. The treatment of angina pectoris of CHD with TBN was significantly more effective compared with the control group (P<0.05). [ABSTRACT FROM AUTHOR]