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Two semi-alicyclic thermoplastic polyimides (PI) have been prepared from stereoisomeric hydrogenated pyromellitic dianhydrides, including 1S,2R,4S,5R-hydrogenated pyromellitic dianhydride (ccHPMDA or H-PMDA) and 1R,2S,4S,5R-hydrogenated pyromellitic dianhydride (ctHPMDA or Hʹʹ-PMDA) and a fluorine-containing diamine, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (BDAF), respectively. The derived PI-1 (ccHPMDA-BDAF) and PI-2 (ctHPMDA-BDAF) resins were easily soluble in polar aprotic solvents, such as N-methyl-2-pyrrolidinone (NMP) and N,N-dimethylacetamide (DMAc) and meanwhile they also exhibited good thermoplasticities. Thus, the PI films (thickness: ~25 μm) and sheets (thickness: ~3 mm) were separately prepared from the PI solutions in DMAc and the PI powders, respectively. The stereoisomeric effects in the ccHPMDA-derived PI-1 and the ctHPMDA-derived PI-2 apparently affected the melt-flowability of the polymers. PI-2 exhibited lower melting viscosities than that of the PI-1 counterpart. The PI sheets exhibited obviously reduced optical transparency compared with those of the PI films; however better optical transparency than those of the common thermoplastic PI sheets. For example, PI-2 sheet showed the optical transmittance value at the wavelength of 760 nm (T760) of 69.6%, which was 19.5% lower than that of the analogous PI-2 film (T760 = 89.1%), however 50.3% and 65.7% higher than those of the commercially available PI-ref1 sheet (T760 = 19.3%) derived from 3,3ʹ,4,4ʹ-oxydiphthalic dianhydride (ODPA) and 4,4ʹ-oxydianiline (ODA) and the PI-ref2 sheet (T760 = 3.9%, Aurum® PL450C, Mitsui Chem. Co, Ltd., Japan), respectively. Meanwhile, the PI-1 and PI-2 sheets showed the heat deflection temperatures (HDT) of 261.0 °C and 265.0 °C, respectively, which were obviously higher than those of the referenced PIs. At last, the PI sheets exhibited good mechanical properties, including high flexural strength (130.0 ~ 132.0 MPa), flexural modulus (2.87 ~ 2.96 GPa), compression strength (124.4 ~ 149.3 MPa), compression modulus (1.49 ~ 1.59 GPa), and impact strength (129.0 ~ 139.6 KJ/m2). [ABSTRACT FROM AUTHOR]

As a promising technology to enable effective multi-modal transmission over wireless channels, semantic communication has attracted a lot of attention from academics and industries. Different from Shannon’s information theory, based on common background knowledge provided by the knowledge base, the goal of semantic communication is transmitting intended useful information from the transmitter and recovered by the receiver at the semantic level. However, the existing studies on semantic communication rarely emphasize the essence and the usage of the knowledge base. In this paper, we propose a knowledge-enhanced semantic communication (KESC) system, where the knowledge base is cloud-edge-device collaborative cached. To solve the problem that float-type symbols are difficult to transmit directly through a radio frequency (RF) system, we adopt orthogonal frequency division multiplexing (OFDM) to transmit semantic vectors directly without some traditional signal processing techniques in semantic information transmission, and the semantic pilot is designed to assist semantic reception. Furthermore, we formulate a multi-encoder transformer based neural network model for the KESC system to support text transmission (KESC-T), where the decoder is implemented with a knowledge graph to enhance the performance of semantic decoding. Besides, we define knowledge-enhanced efficiency (KEE) to measure the gain in semantic recovery accuracy brought by per unit of knowledge. Simulation results demonstrate that the recovery accuracy of our proposed KESC outperforms the compared scheme, especially in low signal-to-noise ratio (SNR) or resource-constrained scenarios. [ABSTRACT FROM AUTHOR]

A new cis-caffeoyl coumarin glycoside, cichorigenin-5-O-(4′-cis-caffeoyl)-β-D-glucopyranoside (1), wasisolated from the stem barks of Fraxinus depauperata, together with two known coumarins, cichorigenin (2) and esculin (3). The chemical structures of compounds 1-3 were elucidated through spectroscopic and chemical analysis, as well as by comparison with the literature. Compounds 2 and 3 are reported from this species for the first time. [ABSTRACT FROM AUTHOR]

Aims/hypothesis: O-GlcNAcylation is implicated in modulating mitochondrial function, which is closely involved in regulating muscle metabolism. The presence of O-GlcNAcase (OGA), the enzyme involved in the removal of O-GlcNAc, in mitochondria was recently confirmed in rats. In the present study, we investigated the regulation of myogenesis and muscle insulin sensitivity to OGA in mice, with a focus on mitochondria. Methods: C57BL/6J mice fed a high-fat diet for 4 months were used to observe mitochondrial density, activity and O-GlcNAcylation in muscle. Small interfering RNA and overexpression vectors were used to modulate protein content in vitro. Results: High-fat feeding decreased the OGA level and largely increased mitochondrial O-GlcNAcylation in mouse skeletal muscle that was accompanied by decreased levels of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), decreased mitochondrial density and disrupted mitochondrial complex activities. Knockdown of OGA in C2C12 myoblasts promoted PGC-1α degradation, resulting in the suppression of mitochondrial biogenesis and myogenesis, whereas neither knockdown of O-GlcNAc transferase nor overexpression of OGA had significant effects on myogenesis. Mitochondrial dysfunction as evidenced by decreased ATP content and increased reactive oxygen species production, and increased lipid and protein oxidation was observed in both myoblasts and myotubes after OGA knockdown. Meanwhile, elevated O-GlcNAcylation through either OGA knockdown or treatment with the OGA inhibitor PUGNAc and the O-GlcNAc transferase substrate d-GlcNAc suppressed myotube insulin signalling transduction and glucose uptake. OGA overexpression had no significant effect on insulin sensitivity but sufficiently improved the insulin resistance induced by d-GlcNAc treatment. Conclusions/interpretation: These data suggest that OGA can modulate mitochondrial density via PGC-1α and mitochondrial function via protein O-GlcNAcylation. In this manner, OGA appears to play a key role in myogenesis and the development of muscle insulin resistance. [ABSTRACT FROM AUTHOR]